Showing posts with label DNA. Show all posts
Showing posts with label DNA. Show all posts
11.09.2008
DNA restriction fragment length polymorphism analysis
In the human genome, an average of about 200 base pair mutation can occur (known as the neutral mutation), neutral mutations lead to inter-individual differences in the nucleotide sequence, referred to as DNA polymorphism. DNA polymorphism occurred in a number of restriction enzyme recognition site, the enzyme will have a length of DNA fragments of different fragments, known as restriction fragment length polymorphism (RFLP). RFLR by way of Mendelian genetics, in a particular family, if a particular gene and disease-specific fragment polymorphism closely linked, polymorphic fragments that can be used as a form of "genetic markers" to judge family members or Whether the fetus for disease gene carriers. Type A hemophilia, cystic fibrosis and phenylketonuria, and so on can be diagnosed using this method.
Single-stranded DNA
Single-stranded DNA (single-stranded DNA) to most of the DNA double helix structure, but once or heat processing base will become a single-stranded state. Single-stranded DNA refers to the existence of such a state of the DNA. Single-stranded DNA molecule in the fluid nature of the absorption spectrum, the base nature of the response, and so on are different and the double-stranded DNA. Some of the phage particle contains a single circular chain of DNA, this kind of phage DNA in the cell proliferation when the formation of double-stranded DNA.
DNA replication
DNA replication is the double-stranded DNA in the cell division process before replication, copy results of a double-stranded into the same two double-stranded (if it is to copy the normal course of the case), each with double-stranded, like the original double-stranded . This process is known as the semi-replication mechanism to enable the successful completion of the. Copy can be divided into the following phases:
Start-up phase: helicase in the local launch of the double helix structure of DNA single-strand molecule, primer-identification initiation site in order to remove a section of DNA as a template, in accordance with the 5 'to 3' direction of short-chain RNA synthesis. The formation of RNA primer.
DNA fragment generation: to provide a primer 3'-OH on the basis of the end, DNA polymerase chain two catalytic DNA replication at the same time, as the process can only be copied by the 5'-> 3 'direction of synthesis, so a chain Can be synthesized in a row, another sub-chain synthesis, in which every chain has become a short Okazaki fragments (Okazaki fragments).
Hydrolysis of RNA primer: When DNA synthesis after a certain length, DNA polymerase hydrolysis of RNA primer, Butian gap.
DNA ligase will fragment of DNA phosphodiester bond linking it to complete the formation of the DNA molecule.
Finally, the new synthetic DNA fragments of the enzyme in the rotation with the help of re-forming spiral.
Start-up phase: helicase in the local launch of the double helix structure of DNA single-strand molecule, primer-identification initiation site in order to remove a section of DNA as a template, in accordance with the 5 'to 3' direction of short-chain RNA synthesis. The formation of RNA primer.
DNA fragment generation: to provide a primer 3'-OH on the basis of the end, DNA polymerase chain two catalytic DNA replication at the same time, as the process can only be copied by the 5'-> 3 'direction of synthesis, so a chain Can be synthesized in a row, another sub-chain synthesis, in which every chain has become a short Okazaki fragments (Okazaki fragments).
Hydrolysis of RNA primer: When DNA synthesis after a certain length, DNA polymerase hydrolysis of RNA primer, Butian gap.
DNA ligase will fragment of DNA phosphodiester bond linking it to complete the formation of the DNA molecule.
Finally, the new synthetic DNA fragments of the enzyme in the rotation with the help of re-forming spiral.
DNA repair
DNA repair (DNA repairing) is a cell of DNA damage after a reaction could resume as the structure of DNA, can be re-implementation of its original features; but sometimes can not completely eliminate the DNA damage, cells can only make This tolerance of DNA damage and can continue to survive. Perhaps this has not been fully repaired and hold down the damage will be suitable for the conditions shown (for example, the cancerous cells, etc.), but if it does not have the cell repair, will not be able to deal with often occur in the DNA damage, to survive . Therefore, DNA repair is also a study to explore an important aspect of life, and military medicine, oncology, and other closely related. Different DNA damage, cells may have different reactions to repair.
DNA contains A, C, G, T four bases, usually A - T, C - G combination of DNA base pairs constitute a chain of cross-file. Gene is to interpret these DNA base pairs in order to convey instructions to the cell to control the work of the cell.
A number of factors give rise to DNA strand breaks, DNA chain restructuring in the base to be re-arranged, reading led to the gene sequences of the original and different, send the wrong order, resulting in the wrong cell growth and, therefore, occurred in the cell mutation, Would also have had a tumor cells. Tumor cells will absorb a large number of nutrients to the body or the fast-growing normal cells and therefore tumor cells than normal cells to be a big, big nuclear 1-5 times higher than normal and more abnormal occurrence, and so on. At the same time, the tumor DNA chain in the same situation will be broken, because with its own DNA repair and a half to retain the function of reproduction, DNA ligase can be re-link the DNA fragments in the rotation to enzymes under the spiral form. And a small section of the DNA of tumor cells can be genetic characteristics of the new generation of tumor cells. Now scientists are often referred to cloning, the DNA is the use of the properties. Therefore, the majority of cases, the tumor DNA chain restructuring is a change two or more of a change process, which the formation of tumor cells to copy and reproduction, which caused the expansion of the tumor, proliferation, transfer and deterioration of the ultimate threat to human health And life.
DNA contains A, C, G, T four bases, usually A - T, C - G combination of DNA base pairs constitute a chain of cross-file. Gene is to interpret these DNA base pairs in order to convey instructions to the cell to control the work of the cell.
A number of factors give rise to DNA strand breaks, DNA chain restructuring in the base to be re-arranged, reading led to the gene sequences of the original and different, send the wrong order, resulting in the wrong cell growth and, therefore, occurred in the cell mutation, Would also have had a tumor cells. Tumor cells will absorb a large number of nutrients to the body or the fast-growing normal cells and therefore tumor cells than normal cells to be a big, big nuclear 1-5 times higher than normal and more abnormal occurrence, and so on. At the same time, the tumor DNA chain in the same situation will be broken, because with its own DNA repair and a half to retain the function of reproduction, DNA ligase can be re-link the DNA fragments in the rotation to enzymes under the spiral form. And a small section of the DNA of tumor cells can be genetic characteristics of the new generation of tumor cells. Now scientists are often referred to cloning, the DNA is the use of the properties. Therefore, the majority of cases, the tumor DNA chain restructuring is a change two or more of a change process, which the formation of tumor cells to copy and reproduction, which caused the expansion of the tumor, proliferation, transfer and deterioration of the ultimate threat to human health And life.
DNA probe
DNA probe is the most commonly used DNA probe, saying that a few hundred base pairs in length than the double-stranded DNA or single-stranded DNA probe. DNA probe has been a lot of volume, there are bacteria, viruses, protozoa, fungi, animals and human cell DNA probe. Such probes for more than a gene sequence in whole or in part, or a non-coding sequences. These DNA fragments is to be specific, such as bacterial virulence factors and human probe gene Alu probe. These DNA probe was dependent on the molecular cloning technology and applications. By bacteria, for example, the current hybridization for bacterial classification and identification of bacteria than the percentage of the value of G + C to be more accurate, is a bacterial taxonomy development. In addition, hybridization of high sensitivity of the hybridization in clinical diagnosis of micro-organisms has broad prospects. The bacterial genome size of about 5 × 106bp, with about 3,000 genes. The vast majority of among a variety of bacterial DNA is the same, it is necessary to obtain a bacteria-specific DNA probe is usually taken to the establishment of bacterial genomic DNA library of the way, is about to bacterial DNA into small fragments were cloned to be included in post-genome-wide information Cloning library. And then use a variety of other strains of DNA probe for screening to produce hybrid cloning signals were taken out, the last remaining non-hybrid with any other bacterial cloning may contain the bacteria-specific DNA fragment. This recombinant plasmid probe after further identification tags can also be identified by DNA sequence analysis of their genetic origin and function. Therefore, to be a specific DNA probe, is more often tedious. Cloning DNA probes can also filter the serological method, the difference is that the library to be built DNA expression, cloning colony or plaque by cracking after the release of antigen expression, then the source of the bacteria polyclonal anti-serum screening positive Cloning, the positive clones from a number of other bacteria to be passed by the anti-serum screening, only with the bacteria response to the expression of anti-serum that contains the bacterial cloning of specific gene fragments, it is the protein encoded by the strain-specific . Using this expression library screening to be clear that only the specific gene probe.
Junk DNA
Yeast and worms like how simple biological evolution for birds and mammals such complex biological ones? A genome extensive comparative study shows that the answer may be hidden in junk DNA organisms (DNA) in. U.S. scientists found that the more complex biological, and its junk DNA to carry more, but rather they not have the code "useless" DNA help of higher evolution of a complex organism.
Since the first eukaryotes - from yeast to the human nucleus of the biological - the genome has been deciphered, scientists have wanted to know why the majority of biological DNA does not form a useful gene. From protection to chromosome mutation of the support structure for the so-called junk DNA may be the explanation of many species. But last year, from humans, mice and rats who received exactly the same garbage on the DNA findings show that this region may contain an important adjustment mechanism in order to be able to control the basis of biochemical reactions and the development process, This will help the evolution of more complex organisms. And simple eukaryotes, more complex biological gene mutation does not occur the fact that no doubt greatly strengthened this discovery.
In order for this problem have a better understanding of the United States by the University of California, Santa Cruz (UCSC) calculation biologist David Haussler of the leadership of a study group of vertebrates 5 -, mice, rats , Chicken and the Blowfish - the junk DNA sequences and 4 types of insects, worms and two 7 junk DNA sequence of yeast were compared. The researchers compared the results obtained from a surprising pattern: The more complex biological, it seems that the more important junk DNA.
This implied the possibility that if different kinds of biological have the same DNA, then the DNA must be used to solve some key issues. Yeast and vertebrates share a certain amount of DNA, after all, they need to create proteins, but only 15% of the total DNA has nothing to do with genes. In the study group on July 14 of "Genome Research," Journal online reported that they would yeast and more complex worms are compared, which is a multi-cell organisms, have found that 40% of the total DNA was not Coding. Subsequently, the researchers also insects and invertebrates were compared, the worm is more complex than the biological and found that more than 66% of the total did not include DNA-encoded DNA.
The study involved in the work of the UCSC biologist Adam Siepel calculated that the worm's findings need to be treated carefully, because scientists have only two genomes were analyzed. Even so, Siepel still believe that this discovery strongly supports such a theory, that is, insects and invertebrates of the biological complexity of the increase was mainly due to the delicate pattern of gene regulation.
Since the first eukaryotes - from yeast to the human nucleus of the biological - the genome has been deciphered, scientists have wanted to know why the majority of biological DNA does not form a useful gene. From protection to chromosome mutation of the support structure for the so-called junk DNA may be the explanation of many species. But last year, from humans, mice and rats who received exactly the same garbage on the DNA findings show that this region may contain an important adjustment mechanism in order to be able to control the basis of biochemical reactions and the development process, This will help the evolution of more complex organisms. And simple eukaryotes, more complex biological gene mutation does not occur the fact that no doubt greatly strengthened this discovery.
In order for this problem have a better understanding of the United States by the University of California, Santa Cruz (UCSC) calculation biologist David Haussler of the leadership of a study group of vertebrates 5 -, mice, rats , Chicken and the Blowfish - the junk DNA sequences and 4 types of insects, worms and two 7 junk DNA sequence of yeast were compared. The researchers compared the results obtained from a surprising pattern: The more complex biological, it seems that the more important junk DNA.
This implied the possibility that if different kinds of biological have the same DNA, then the DNA must be used to solve some key issues. Yeast and vertebrates share a certain amount of DNA, after all, they need to create proteins, but only 15% of the total DNA has nothing to do with genes. In the study group on July 14 of "Genome Research," Journal online reported that they would yeast and more complex worms are compared, which is a multi-cell organisms, have found that 40% of the total DNA was not Coding. Subsequently, the researchers also insects and invertebrates were compared, the worm is more complex than the biological and found that more than 66% of the total did not include DNA-encoded DNA.
The study involved in the work of the UCSC biologist Adam Siepel calculated that the worm's findings need to be treated carefully, because scientists have only two genomes were analyzed. Even so, Siepel still believe that this discovery strongly supports such a theory, that is, insects and invertebrates of the biological complexity of the increase was mainly due to the delicate pattern of gene regulation.
Plasmid DNA of speeding centrifuge latest developments
(1) turn their back on the tube vertical speed centrifuge (Chin alloys or carbon fiber-made): From 1975 to the vertical pipe turned the world, in recent years, the major manufacturer of centrifuges developed in a vertical tube the other way round, single-tube capacity of 0.2 ml to 4Oml, the maximum speed from 50000rpm to 120000rpm, RCFmax up to 700, OOOXg, 90 during the development of new models and has been able to turn their back on plasmid DNA vertical centrifuge tube experiments done easier.
(3) near vertical turn their back on centrifuge tubes: In order to eliminate the vertical pipe used to turn their back on the plasmid DNA in the centrifugal wall formed by the Ministry of RNA precipitation of DNA has become the zone of pollution, but also to improve the general-turned beveled (Dip 25 • - 35 •) due to the settlement of a long distance, which separated from the shortcomings of a longer time in the last few years has developed a variety of vertical pipe near the other way round (that is, Near VerticalTube Rot, or turn their back on NVT referred to as Neo Angle Rotor, leave a small angle turn, referred to as NT). Centrifuge tube section of the central axis and the angle between the axis centrifuge drive in the 7.5 • - 10 •, from the speed 65000rpm to 120, OOOrpm, RCFmax can 646000 × g up to one-tube capacity from 2ml to 13.5ml. NVT (or NT) turned mainly to the development of the plasmid DNA and the separation of design, of course, it also applies to mitochondrial DNA, chromosome DNA, RNA and serum lipoprotein • separation and purification.
(3) non-continuous gradient separation step: school quality DNA isolation and purification method is the traditional gold formed tube from CsCl density gradient centrifugation, and so on balance, beginning of the centrifuge tube CsCl gold uniform density, samples of which uniformly distributed.
(3) near vertical turn their back on centrifuge tubes: In order to eliminate the vertical pipe used to turn their back on the plasmid DNA in the centrifugal wall formed by the Ministry of RNA precipitation of DNA has become the zone of pollution, but also to improve the general-turned beveled (Dip 25 • - 35 •) due to the settlement of a long distance, which separated from the shortcomings of a longer time in the last few years has developed a variety of vertical pipe near the other way round (that is, Near VerticalTube Rot, or turn their back on NVT referred to as Neo Angle Rotor, leave a small angle turn, referred to as NT). Centrifuge tube section of the central axis and the angle between the axis centrifuge drive in the 7.5 • - 10 •, from the speed 65000rpm to 120, OOOrpm, RCFmax can 646000 × g up to one-tube capacity from 2ml to 13.5ml. NVT (or NT) turned mainly to the development of the plasmid DNA and the separation of design, of course, it also applies to mitochondrial DNA, chromosome DNA, RNA and serum lipoprotein • separation and purification.
(3) non-continuous gradient separation step: school quality DNA isolation and purification method is the traditional gold formed tube from CsCl density gradient centrifugation, and so on balance, beginning of the centrifuge tube CsCl gold uniform density, samples of which uniformly distributed.
Plasmid DNA ultracentrifugation separation method
Traditional methods of separation: A few years ago, because of equipment limitations, the plasmid DNA isolated by the general balance CsCl density centrifugation, since the formation of gradient. 10 ~ 12ml to one-tube capacity, for example, turned-off by the separation, 36.000rpm × 60 hours, with angle-separation turned 45, OOOrpm × 36 hours, including the former deceleration, spent a total of 130,000,000 to drive the Ministry of life , Who also used to drive the Department of 100,000,000 life, which is speeding at the time of the total life span of 100 centrifuges to 20,000,000,000 turn, no doubt the cost of each experiment is too high, and the amount of CsCl, your price and other factors, So that the separation and purification of such work has become very expensive experiment.
DNA ultracentrifugation
Modern separation and purification of plasmid DNA from E. coli isolated as representative of the overall situation in view of the bacteria (E.coli) in the molecular biology of the important status of E.coli isolated from purified DNA quality control has become in recent years Ultra-centrifuge technology is an important subject. The plasmid DNA of the rapid separation and purification of the ultra-centrifuge equipment (centrifuges speeding, turned and ancillary equipment) has put forward higher requirements.
E.coli is typical of the original cell biology, because of its lack of prokaryotic cell by cell with a unit from the kind of film composed of a variety of functions can be divided into specific components of the local and regional independent system of the endometrium, Therefore not included in his cell the cell (nucleus, endoplasmic reticulum, Golgi, the line and Latin America, lysosome, and so on). SEM micrographs showed that E.coli can have two distinct regions within each of the cytoplasm and nuclear in nature, in their thin layer around the outside of the cell membrane and very thick walls, some attached to the outside wall at the end of the free Flagellum. Plasmid DNA is located in the nuclear area, so as to the existence of thin filament, the filament-like in many cases is a very long loop of DNA fragments by a number of folded-up-close.
E.coli for the micro-structure of the question, in ultra-centrifugal separation and purification of plasmid DNA prior to the pre-order are:
E.coli → → cell wall with lysozyme to use surfactants such as SDS, Trit X-100 cell membrane, such as EE → pot with acetic acid to make DNA, RNA and protein most of the precipitation (90%).
Sediments can join the TE buffer (10m-MTris-HCL lmMEDTA, pH8.0) after the molecular sieve to live on protein to RNA; can also be used ultracentrifugation to-home, to RNA, or DNA-like class to DNA fragment .
E.coli is typical of the original cell biology, because of its lack of prokaryotic cell by cell with a unit from the kind of film composed of a variety of functions can be divided into specific components of the local and regional independent system of the endometrium, Therefore not included in his cell the cell (nucleus, endoplasmic reticulum, Golgi, the line and Latin America, lysosome, and so on). SEM micrographs showed that E.coli can have two distinct regions within each of the cytoplasm and nuclear in nature, in their thin layer around the outside of the cell membrane and very thick walls, some attached to the outside wall at the end of the free Flagellum. Plasmid DNA is located in the nuclear area, so as to the existence of thin filament, the filament-like in many cases is a very long loop of DNA fragments by a number of folded-up-close.
E.coli for the micro-structure of the question, in ultra-centrifugal separation and purification of plasmid DNA prior to the pre-order are:
E.coli → → cell wall with lysozyme to use surfactants such as SDS, Trit X-100 cell membrane, such as EE → pot with acetic acid to make DNA, RNA and protein most of the precipitation (90%).
Sediments can join the TE buffer (10m-MTris-HCL lmMEDTA, pH8.0) after the molecular sieve to live on protein to RNA; can also be used ultracentrifugation to-home, to RNA, or DNA-like class to DNA fragment .
DNA paternity testing
What is a DNA paternity test test?
DNA (deoxyribonucleic acid) is a personal cell in the body of the atomic material. Each atom has 46 chromosomes, while men's sperm cells and female egg, each with 23 chromosomes, when sperm and egg. This 46 atoms to create a life on the chromosome, each from a father who inherited half of the material elements, while the other half received from the mother.
DNA paternity testing testing with the traditional blood tests are quite different. It can be carried out on samples of different tests, including blood, gill chamber cell, tissue and cell samples of semen samples. As the blood type, such as A-, B-, O-or-RH, the crowd of more common use, used to tell everyone's blood, but not as effective test DNA paternity testing. In addition to the real twins, each person's DNA is unique. Because it is so unique, like fingerprints, for paternity testing, DNA is the most effective way. We are often the result than the court also called for an accurate 1-10-fold.
The accuracy of the paternity test
DNA paternity testing is the most accurate paternity test method, if a child's genetic test site and the site of the man (at least a) inconsistent, then the man will be 100% excluded from blood relationship, that is, he can not May be the father of the child. If the children and their parents are in line site, we will be able to come to the relationship between parental authority is greater than 99.99 percent of the possibility that their blood to prove parent-child relationship.
Parentage testing must (1) were identified by the mother - son - the father or suspicious parents - children, only the mother or father and son duo Jian Dingzhe generally inadmissible; (2) per adult to be identified agreed that identification should be voluntary, 12 Over the age of young people should be seeking to identify their views; (3) identification should be aware of their close relatives or whether the genetic history; (4) have been identified in children aged six months or more for the general good; (5) or amniotic fluid Villus paternity testing for pregnant women and should be commissioned to identify suspicious father signed the agreement.
DNA (deoxyribonucleic acid) is a personal cell in the body of the atomic material. Each atom has 46 chromosomes, while men's sperm cells and female egg, each with 23 chromosomes, when sperm and egg. This 46 atoms to create a life on the chromosome, each from a father who inherited half of the material elements, while the other half received from the mother.
DNA paternity testing testing with the traditional blood tests are quite different. It can be carried out on samples of different tests, including blood, gill chamber cell, tissue and cell samples of semen samples. As the blood type, such as A-, B-, O-or-RH, the crowd of more common use, used to tell everyone's blood, but not as effective test DNA paternity testing. In addition to the real twins, each person's DNA is unique. Because it is so unique, like fingerprints, for paternity testing, DNA is the most effective way. We are often the result than the court also called for an accurate 1-10-fold.
The accuracy of the paternity test
DNA paternity testing is the most accurate paternity test method, if a child's genetic test site and the site of the man (at least a) inconsistent, then the man will be 100% excluded from blood relationship, that is, he can not May be the father of the child. If the children and their parents are in line site, we will be able to come to the relationship between parental authority is greater than 99.99 percent of the possibility that their blood to prove parent-child relationship.
Parentage testing must (1) were identified by the mother - son - the father or suspicious parents - children, only the mother or father and son duo Jian Dingzhe generally inadmissible; (2) per adult to be identified agreed that identification should be voluntary, 12 Over the age of young people should be seeking to identify their views; (3) identification should be aware of their close relatives or whether the genetic history; (4) have been identified in children aged six months or more for the general good; (5) or amniotic fluid Villus paternity testing for pregnant women and should be commissioned to identify suspicious father signed the agreement.
Scientists found that in addition to the DNA genetic code in addition to the new password
According to Taiwan media reports, the United States and Israel scientists believe they have DNA (deoxyribonucleic acid) in addition to the genetic code to find outside of the second password. The newly discovered password ─ body responsible for deciding on the nuclear DNA that is the miniature protein spools around ─ the location. These spools at the same time protect and control access to DNA itself.
This finding, if confirmed, could open the control of gene related to higher-order bit of the new mechanism. For example, every human cell to activate the genes it needs but can not touch on other types of cells used in gene and so is also the key to the mysterious process.
Israel's Weizmann Institute of Northwestern University and saqr the Witton and his colleagues in this "natural" scientific journals, the author describes the DNA of this new password.
Every cell in the human body has about 30,000,000 nuclear body. The reason why it has taken so many nuclear, because the DNA-coated line for each of a nuclear-only. 65 times on each of the DNA helix that contains 147 units, and a single chromosome's DNA molecule at length on There may be up to 225,000,000 units.
Biologists suspect that over the years, DNA on some of the locations, in particular, DNA is most likely to bend to those locations, other than the location more conducive to the existence of the nuclear body, but the overall pattern is not obvious. Today, the witton Dr. saqr and analysis of the yeast gene location within about 200 of the series, knows these are entangled with the nuclear body, found two really implied the existence of a pattern.
Through the understanding of this model, they predict the success of other organisms into some five nuclear body. This model is easier to allow DNA bending, as well as the close of the package review body combination of the two series. However, in this mode, the Each nuclear-entangled only the location of a number of sequences can occur, it is not clear. It is precisely because of its loose formation conditions, it does not conflict with the genetic code.
This finding, if confirmed, could open the control of gene related to higher-order bit of the new mechanism. For example, every human cell to activate the genes it needs but can not touch on other types of cells used in gene and so is also the key to the mysterious process.
Israel's Weizmann Institute of Northwestern University and saqr the Witton and his colleagues in this "natural" scientific journals, the author describes the DNA of this new password.
Every cell in the human body has about 30,000,000 nuclear body. The reason why it has taken so many nuclear, because the DNA-coated line for each of a nuclear-only. 65 times on each of the DNA helix that contains 147 units, and a single chromosome's DNA molecule at length on There may be up to 225,000,000 units.
Biologists suspect that over the years, DNA on some of the locations, in particular, DNA is most likely to bend to those locations, other than the location more conducive to the existence of the nuclear body, but the overall pattern is not obvious. Today, the witton Dr. saqr and analysis of the yeast gene location within about 200 of the series, knows these are entangled with the nuclear body, found two really implied the existence of a pattern.
Through the understanding of this model, they predict the success of other organisms into some five nuclear body. This model is easier to allow DNA bending, as well as the close of the package review body combination of the two series. However, in this mode, the Each nuclear-entangled only the location of a number of sequences can occur, it is not clear. It is precisely because of its loose formation conditions, it does not conflict with the genetic code.
Recombinant DNA technology
In the 1950s, DNA double helix structure was clear that opened a new chapter in the life sciences, opened up a new era of science and technology. Subsequently, the molecular mechanism of genetic - DNA replication, the genetic code, the genetic information of the central dogma, as the basic unit of genetic engineering and cell's genetic blueprint, as well as the regulation of gene expression have been recognized. So far, people have been fully aware of the fate of all living things is that it contains DNA and genes, biological evolution and life processes are different, because the DNA is the genetic and operation of the track due to a difference.
DNA know the important role and value of, first of all life scientists can think of certain human interests are closely related to the genetic aspects of the natural break the iron rule of asking the patients to turn over a new leaf of the gene to achieve the purpose of medical treatment, the genes from different sources Fragment "grafted" to produce new varieties and new quality ... ... As a result, one full of attractive science fiction miraculously become a reality. This is a place in the early 1970s.
The realization of the scientific miracles of science and technology is a means of recombinant DNA technology. In 1972, American scientists Paul? Burg for the first time succeeded in restructuring the world's first batch of DNA molecule, marking the recombinant DNA technology - genetic engineering as the basis of modern bio-engineering, modern biotechnology and life science foundation and core .
Recombinant DNA technology is the specific content of artificial means to different sources with a particular gene's DNA fragment to restructure in order to achieve the biological changes in gene type and specific purpose of the gene product of a high science and technology.
By the 1970s the mid-and late, as a result of the realization of the project, as well as bacteria after DNA and re-engineered to deal with both the nature of genetic engineering or recombinant DNA as the genetic engineering technology is widely used synonym. Now, genetic engineering also includes the transformation of the genome, nucleic acid sequence analysis, molecular evolution, molecular immunology, gene cloning, gene diagnosis and gene therapy and so on. It can be said, DNA recombinant technology to create the past 30 years obtained fruitful results it has brought them to a mysterious dream-like world of science, mankind was to open the mysteries of life and to prevent and cure diseases, "Box" golden key .
At present, DNA recombinant technology has been achieved by many factors. To the end of the 20th century, DNA recombinant technology in the field of application of the largest Chinese medicine, including active peptides, proteins and vaccine production, disease pathogenesis, diagnosis and treatment, the new gene, as well as environmental monitoring of separation and purification.
Many active peptides and proteins have the treatment and prevention of diseases, they are all from the corresponding gene's arise. However, in cells with minimal output, the conventional method is difficult to get enough volume for clinical application.
Genetic engineering breakthroughs are the limitations of this type can be mass-produced peptides and proteins, so far has successfully produced the treatment of diabetes and insulin schizophrenia, cancer of the blood and solid tumors have a certain effect of antiviral agents -- Interferon, human growth hormone treatment of dwarfism, acromegaly treatment of acute pancreatitis and the release of growth hormone inhibitor, such as more than 100 kinds of products.
Genetic engineering may also be related antigen into the DNA of living microorganisms, such micro-organisms in the host immune stress in the body can produce the growth of live attenuated vaccines, with a large dose of antigen stimulation, and lasted for a long time, and other advantages. Is currently being developed genetically engineered vaccine will have as many as dozens, have to deal with bacteria for bacteria leprosy, Bordetella pertussis, Neisseria gonorrhoeae, such as the meningococcal vaccine; in the fight against the virus have against hepatitis A, hepatitis B , Cytomegalovirus, herpes simplex, influenza, human immunodeficiency virus vaccines, and so on ... .... China's hepatitis B virus carriers of hepatitis B patients and as many as Yier Yi, the situation is even more promoting China's own scientists have successfully developed the hepatitis B vaccine, has made great social and economic benefits.
Antibodies are the body's immune system disease resistance of one of the main weapons, the 1970 creation of the monoclonal antibody technology in the aspects of disease prevention has played an important role, but it is difficult to obtain human-derived monoclonal antibody, making single - Anti-clinical application is limited. To address the problem, in recent years, scientists using recombinant DNA technology has been derived human antibody, the antibody can guarantee it with the combination of antigen specificity and affinity, but also ensures that the normal function of the play. At present, such a variety of antibodies in clinical trials carried out, such as anti-HER-2 humanized monoclonal antibody treatment of breast cancer has entered Phase Ⅲ, anti-IGE humanized monoclonal antibody treatment of asthma has entered Phase Ⅱ.
Antibiotics in the treatment of the disease has played an important role, with the increase in the number of antibiotics, use traditional methods to discover new antibiotics are becoming less and less likely. In order to get more new antibiotics, the use of recombinant DNA technology has become an important means. At present, there have been dozens of genetic engineering "hybrid" of antibiotics for clinical application has opened up new avenues of treatment.
It is worth noting that the above genetically engineered peptides, proteins, vaccines, antibiotics, such as drug prevention and treatment, not only in effective control of the disease, but also to avoid the side effects are also often better than the traditional method of production of similar drugs, so more people favor .
Human diseases are directly or indirectly associated with the gene, the gene in the level of disease diagnosis and treatment can reach the accuracy of the diagnosis of the cause and nature of the original, diagnosis and treatment can work to achieve specific, sensitive and easy Fast. At the level of gene diagnosis and treatment in the gene known as a professional diagnosis and gene therapy. At present, genetic diagnosis as a fourth-generation clinical diagnostic techniques have been widely used for genetic diseases, cancer, cardiovascular and cerebrovascular diseases, viruses and bacterial diseases such as parasitic disease diagnosis; and the goal of gene therapy is through DNA recombinant technology to create a Specific features of the recombinant gene to compensate for the loss of function in the role of the gene, or a function for the benefit of an increase of abnormal cells to correct or eliminate.
In theory, a permanent cure is gene therapy to cure without any side effects of therapy. However, despite the international community has been more than 100 gene therapy program is in clinical trials, gene therapy in theory and in a number of technical problems remain to make this treatment from a large-scale application there is a long distance. Whether genes determine the cause or the implementation of gene diagnosis, gene therapy, the study of the mechanism of disease, a key prerequisite to understand the specific disease-related genes. With the "Human Genome Project," is approaching completion, the scientists of all human genes will get a complete picture, which was made using recombinant technology to force in the cause of human health to create conditions.
However, although the human gene technology to display its wonderful "Magic"-like charm, but there are a large number of scientists on the development of this technology to human ethics and ecological evolution of the impact of natural law expressed great concern. In theory, this technology is the ultimate development of a human have to create any form of life or biological unprecedented. People can imagine what this will be the outcome?
DNA know the important role and value of, first of all life scientists can think of certain human interests are closely related to the genetic aspects of the natural break the iron rule of asking the patients to turn over a new leaf of the gene to achieve the purpose of medical treatment, the genes from different sources Fragment "grafted" to produce new varieties and new quality ... ... As a result, one full of attractive science fiction miraculously become a reality. This is a place in the early 1970s.
The realization of the scientific miracles of science and technology is a means of recombinant DNA technology. In 1972, American scientists Paul? Burg for the first time succeeded in restructuring the world's first batch of DNA molecule, marking the recombinant DNA technology - genetic engineering as the basis of modern bio-engineering, modern biotechnology and life science foundation and core .
Recombinant DNA technology is the specific content of artificial means to different sources with a particular gene's DNA fragment to restructure in order to achieve the biological changes in gene type and specific purpose of the gene product of a high science and technology.
By the 1970s the mid-and late, as a result of the realization of the project, as well as bacteria after DNA and re-engineered to deal with both the nature of genetic engineering or recombinant DNA as the genetic engineering technology is widely used synonym. Now, genetic engineering also includes the transformation of the genome, nucleic acid sequence analysis, molecular evolution, molecular immunology, gene cloning, gene diagnosis and gene therapy and so on. It can be said, DNA recombinant technology to create the past 30 years obtained fruitful results it has brought them to a mysterious dream-like world of science, mankind was to open the mysteries of life and to prevent and cure diseases, "Box" golden key .
At present, DNA recombinant technology has been achieved by many factors. To the end of the 20th century, DNA recombinant technology in the field of application of the largest Chinese medicine, including active peptides, proteins and vaccine production, disease pathogenesis, diagnosis and treatment, the new gene, as well as environmental monitoring of separation and purification.
Many active peptides and proteins have the treatment and prevention of diseases, they are all from the corresponding gene's arise. However, in cells with minimal output, the conventional method is difficult to get enough volume for clinical application.
Genetic engineering breakthroughs are the limitations of this type can be mass-produced peptides and proteins, so far has successfully produced the treatment of diabetes and insulin schizophrenia, cancer of the blood and solid tumors have a certain effect of antiviral agents -- Interferon, human growth hormone treatment of dwarfism, acromegaly treatment of acute pancreatitis and the release of growth hormone inhibitor, such as more than 100 kinds of products.
Genetic engineering may also be related antigen into the DNA of living microorganisms, such micro-organisms in the host immune stress in the body can produce the growth of live attenuated vaccines, with a large dose of antigen stimulation, and lasted for a long time, and other advantages. Is currently being developed genetically engineered vaccine will have as many as dozens, have to deal with bacteria for bacteria leprosy, Bordetella pertussis, Neisseria gonorrhoeae, such as the meningococcal vaccine; in the fight against the virus have against hepatitis A, hepatitis B , Cytomegalovirus, herpes simplex, influenza, human immunodeficiency virus vaccines, and so on ... .... China's hepatitis B virus carriers of hepatitis B patients and as many as Yier Yi, the situation is even more promoting China's own scientists have successfully developed the hepatitis B vaccine, has made great social and economic benefits.
Antibodies are the body's immune system disease resistance of one of the main weapons, the 1970 creation of the monoclonal antibody technology in the aspects of disease prevention has played an important role, but it is difficult to obtain human-derived monoclonal antibody, making single - Anti-clinical application is limited. To address the problem, in recent years, scientists using recombinant DNA technology has been derived human antibody, the antibody can guarantee it with the combination of antigen specificity and affinity, but also ensures that the normal function of the play. At present, such a variety of antibodies in clinical trials carried out, such as anti-HER-2 humanized monoclonal antibody treatment of breast cancer has entered Phase Ⅲ, anti-IGE humanized monoclonal antibody treatment of asthma has entered Phase Ⅱ.
Antibiotics in the treatment of the disease has played an important role, with the increase in the number of antibiotics, use traditional methods to discover new antibiotics are becoming less and less likely. In order to get more new antibiotics, the use of recombinant DNA technology has become an important means. At present, there have been dozens of genetic engineering "hybrid" of antibiotics for clinical application has opened up new avenues of treatment.
It is worth noting that the above genetically engineered peptides, proteins, vaccines, antibiotics, such as drug prevention and treatment, not only in effective control of the disease, but also to avoid the side effects are also often better than the traditional method of production of similar drugs, so more people favor .
Human diseases are directly or indirectly associated with the gene, the gene in the level of disease diagnosis and treatment can reach the accuracy of the diagnosis of the cause and nature of the original, diagnosis and treatment can work to achieve specific, sensitive and easy Fast. At the level of gene diagnosis and treatment in the gene known as a professional diagnosis and gene therapy. At present, genetic diagnosis as a fourth-generation clinical diagnostic techniques have been widely used for genetic diseases, cancer, cardiovascular and cerebrovascular diseases, viruses and bacterial diseases such as parasitic disease diagnosis; and the goal of gene therapy is through DNA recombinant technology to create a Specific features of the recombinant gene to compensate for the loss of function in the role of the gene, or a function for the benefit of an increase of abnormal cells to correct or eliminate.
In theory, a permanent cure is gene therapy to cure without any side effects of therapy. However, despite the international community has been more than 100 gene therapy program is in clinical trials, gene therapy in theory and in a number of technical problems remain to make this treatment from a large-scale application there is a long distance. Whether genes determine the cause or the implementation of gene diagnosis, gene therapy, the study of the mechanism of disease, a key prerequisite to understand the specific disease-related genes. With the "Human Genome Project," is approaching completion, the scientists of all human genes will get a complete picture, which was made using recombinant technology to force in the cause of human health to create conditions.
However, although the human gene technology to display its wonderful "Magic"-like charm, but there are a large number of scientists on the development of this technology to human ethics and ecological evolution of the impact of natural law expressed great concern. In theory, this technology is the ultimate development of a human have to create any form of life or biological unprecedented. People can imagine what this will be the outcome?
Discovery of DNA
Since Mendel's laws of genetic re-discovered, it also raises the question: is the genetic material is not an entity? In order to solve the problem of what genes are, the people of nucleic acids and proteins.
As early as 1868, people have been found in nucleic acids. Chemists in Germany Hoppe Sailor's lab, a graduate of the Swiss(1844 - 1895), his lab near a hospital threw the bandage with blood of the very sense of Interest, because he knows that those blood to defend human health, germs and "combat" and was killed in action and kill white blood cells of the human body "remains." He carefully put a bandage on the blood collected and used for decomposition of pepsin, and found the bodies of most of the cells break down, but on the nuclear non-functional. He further on the nuclear material within an analysis and found that the nucleus contains a phosphorus and nitrogen-rich material. Hoppe sail with yeast experiments to prove that the material inside the nucleus of the Mitchell findings are correct. He would like to give this separate from the nuclear material is known as "nuclide", was later found that it was acidic, so to be called "nucleic acid." Since then, people have carried out a series of effective nucleic acid.
In the early 20th century, Germany Ke Saier (1853 - 1927) and two of his students Jones (1865 - 1935) and Levin (1869 - 1940) study, understand the basic chemical structure of nucleic acids, it Is composed of a number of nucleotide molecules. By nucleotide base pairs, consisting of phosphate and ribose. There are 4 kinds of bases in which (Yin cast a glance gland, Yin guanine, thymine and cytosine), there are two ribose (ribose, deoxyribose), the nucleic acids into RNA (RNA) and deoxyribonucleic acid (DNA) .
Levin made his rush to the results of research, mistakenly believe that 4 in the nucleic acid bases in the volume is equal, so as to derive the basic structure of nucleic acids by 4 with different nucleotide bases to connect into a four-nucleoside Acid as a basis for nucleic acid into a polymer, a "four-nucleotide hypothesis." This hypothesis wrong, understanding of the complex structure of nucleic acids from the considerable obstacles, to a certain extent affected the people's understanding of the functions of nucleic acids. It is believed that although the nucleic acid present in the structure of the important - nuclear, but its structure is too simple, it is hard to imagine in the process of genetic What role.
Protein nucleic acid than found as early as 30 years, has developed rapidly. Of the 20th century, composed of 20 amino acid protein has been found to be 12, 1940, the whole was found.
In 1902, a German chemist Xie Erti charges between amino acid peptide chain link and the theory of the formation of proteins, in 1917, he was synthesized by the glycine-15 leucine and 3 of the 18 components of long-chain . As a result, some scientists the idea, is likely to be genetic in the protein plays a major role. If the nucleic acids involved in genetic, protein and must be linked to the role of the protein. As a result, at that time generally tend to think that biological protein is the carrier of genetic information.
In 1928, American scientists Griffith (1877 - 1941) with a capsule, and a strong toxic-free capsule, low toxicity of the pneumococcus experiments on rats. To have He pods high temperature to kill bacteria with no along with pods of live bacteria were injected mice, he found that the incidence of death soon rats, mice at the same time he's in the blood of the isolated bacteria living there pod. This shows that even without passing bacteria from the dead bacteria in the pod have access to what material to make a risk-free bacteria into bacteria have a pod. Assuming that the right thing to do? Griffith in a test tube experiment and found the dead bacteria with the United States are living without passing on the bacteria test tube train at the same time, without passing all the bacteria have become a pod bacteria and found so that no bacteria long pod A protein of the scare is there a risk of dead bacteria in the shell left over from the nucleic acid (as in heating, the pod of nucleic acid has not been damaged). Griffith said the nucleic acid as a "conversion factor."
In 1944, the United States Avery bacteriologist (1877 - 1955) from the United States and bacteria have been isolated activity of the "conversion factor", and that such material did a test of the existence of protein test, the results were negative, and to prove "Conversion factor" is the DNA. But this has not been found in a wide range of recognition, it is not suspected at the time of the technology in addition to net protein, the protein residues into play.
German-American scientists Delbruck (1906 - 1981) of phage group has a firm belief that Avery's discovery. Because they observed under the electron microscope of the phage into the shape and growth of E. coli. Phage bacterial cell is a host for the virus, individual small, with only the electron microscope to see it. It is like a small tadpole, the external components of the protein by the end of the first film and the sheath, the head of the internal contain DNA, the end of the end of silk sheath there, the substrate and the small hook. When the phage infection of E. coli, the tail end of the first bar in the bacterial cell membrane, and then it will be all the body's DNA were injected into bacteria cells, the protein shell remain in the bacterial cell outside, not from what the role of the . After the bacteria enter the cells of the phage DNA, on the use of bacterial material and rapid synthesis of the phage DNA and proteins, so many copy of the original size of the display exactly the same shape of a new phage until the bacteria were completely disintegrated, leaving only those phage dead bacteria , And then infect other bacteria.
In 1952, key members of the phage group Hershey (a 1908) and his students use the Chase advanced isotope labeling, so the E. coli bacteriophage experimental infection. He coli T2 phage DNA markers on 32P, the protein shell markings on 35S. Marking the first use of phage T2 E. coli infection, and then be separated from the results of the phage will be marked with 35S shell out to stay in E. coli, only the internal display with a 32P labeled nucleic acid were injected all the E. coli and E. coli within Phage successful breeding. The DNA test to prove there is transmission of genetic information of the functions of proteins and DNA by the synthesis of the directive. The result was immediately accepted by the academic community.
Almost at the same time, Austria biochemist Chargaff (1905 -) of the nucleic acid bases in 4 of the content of the outcome of the re-determination has been made. Avery in the work, if he thought the different species is due to the different DNA, the DNA structure must be very complicated, or difficult to adapt to biological diversity. As a result, he was out of the text "four nucleotide hypothesis," have had a doubt. In the 1948 - 1952 4 years, he made use of Levin times more than the precision of paper chromatography separation of 4 base pairs, with UV absorption spectra to do quantitative analysis, after repeated the experiment many times, and finally arrive at a different Levine. The results show that DNA molecules in purine and pyrimidine equal to the total number of elements, of which purine A gland and an equal number of T thymine, guanine and cytosine G Yin C equal to the number. Description of the DNA molecule A base with T, G and C is the existence of the match, which negates the "four nucleotide hypothesis", as well as to explore the molecular structure of DNA provides an important clue and based on.
April 25, 1953, the United Kingdom's "Nature" magazine published in the United States of Watson and Crick of the British University of Cambridge in cooperation with the results of research: DNA double helix model of the molecule, known as the outcome of the later 20 Century biology's greatest discoveries marked the birth of molecular biology.
Watson (1928 A) in middle school is an extremely intelligent children, 15-year-old when they entered the study at the University of Chicago. At that time, because of a person to allow an earlier study of the experimental sex education programs so that Watson had the opportunity to complete all aspects from the study of biological science courses. At the university, although Watson in genetics have little formal training, but since reading the Schrodinger's "What is life? - The physical appearance of living cells, "which prompted him to" find the genetic secrets. " He was good at brainstorming to win many long, good at using other people's ideas to enrich themselves. As long as there are convenient, do not have to force yourself to a whole new field of study, can be required knowledge. 22-year-old Watson made a doctorate, and then was sent to Europe to pursue post-doctoral researcher. In order to fully understand a gene's chemical structure of the virus, he went to study chemical laboratory in Copenhagen, Denmark. On one occasion he went to Naples, Italy, tutor to take part in a meeting of biological macromolecules, have the opportunity to listen to the British biologist physical Wilkins (1916 -) speech, Wilkins saw the DNAX-ray diffraction photograph. Since then, to find the key to unlock the structure of DNA in Watson's idea in the minds of the return. What can learn X-ray diffraction analysis of this map? So he went to Britain to study at the University of Cambridge Cavendish Laboratory, during which Watson understanding of the creek.
Crick (1916-2004) when high school passion for science, and in 1937 graduated from the University of London. In 1946, he read "What is life? - The physical appearance of living cells ", is determined to use the knowledge of physics to the study of biology, from biology to the interest. In 1947 he re-started the post-graduate study, in 1949, he Perutz used in conjunction with the X-ray study of the technical structure of the protein molecule, so this has been met with Watson. Watson, Crick was more than 12-year-old major, has not yet obtained a doctoral degree. However, very speculative to talk about them, Watson here are actually able to find how a protein is more important than DNA, is Sanshengyouxing. At the same time, Watson was in contact with his people, the creek is one of the most intelligent. They talked every day for at least a few hours to discuss academic issues. The two were complementary with each other to criticize each other, as well as stimulate each other's inspiration. They do not think the answer is to open the molecular structure of DNA genetic key to the mystery. With only the precise X-ray diffraction data in order to more quickly identify the structure of DNA. In order to get DNAX-ray diffraction, Crick invited Wilkins to come to Cambridge for the weekend. In the conversation Wilkins accepted the spiral structure of DNA point of view, but also his partner Franklin (1920-1958, F), as well as lab scientists also have been thinking very hard with the problem of DNA structure model . From from November 1951 to April 1953 for 18 months, Watson, Crick and Wilkins and Franklin are among several important academic exchanges.
In November 1951, after listening to Franklin Watson on the structure of the DNA of a more detailed report, inspired by a certain knowledge of the crystal structure analysis of Watson and Crick realized that in order to quickly establish the structure of DNA model, only Be able to use other people's analysis of the data. They quickly made a three-helical structure of DNA idea. By the end of 1951, they invited Wilkins and Franklin to discuss this model, Franklin pointed out that the water content of their DNA to less than half do so for the first time to set up the model failed.
One day, Watson went to King's College laboratory Wilkins, Wilkins Franklin recently beat out a system of "B-" DNA of the X-ray diffraction photograph. Watson saw pictures of them at once exciting, heart rate has accelerated, such as images than ever before to be the "A" is much more simple, as long as a little look at the "B-" X-ray diffraction photograph, and then by a simple calculation, Will be able to determine the number of DNA molecules in the number of nucleotide chains.
Please help Crick mathematician calculated results show that the source has attracted Yin Fu. According to their results from the Chargaff and got the two nucleic acid purine and pyrimidine two 22 equal As a result, the formation of the concept of base pairs.
They desperately to think of the 4 base sequence, time and again drawing on paper-base structure, playing with the model, repeatedly made the assumption that time and again to overthrow their own assumptions.
Watson (left) and there is a creek, according to Watson in the idea of playing with their own model, he shifted base to search for the removal of all kinds of matching. Suddenly, he found two hydrogen bonds linking the gland Yin-fat thymine and went so far as to the hydrogen bond of 3-connected guanine cytosine-Yin of have the same shape, so it boosted the spirit. Because the number of purine and pyrimidine why the number should be exactly the same as the mystery solved. Chargaff all of a sudden it became the law of DNA double helix structure of the inevitable result of the. As a result, how the chain as a template synthesis of another complementary sequence of bases is not hard to imagine the chain. In that case, the skeleton of the two chains must have the opposite direction.
After Watson and Crick tension in a row, quickly completed a metal model of DNA assembly. From this model to see, DNA from the two components of nucleotide chains, which along with the central axis of intertwined with each other in the opposite direction, much like a spiral staircase handrails on both sides is more than 2 nucleotide chains P-glycoprotein gene combined with the turn of the skeleton, and the pedal base is right. In the absence of accurate information on X-ray, they dare not conclude that the model is entirely correct.
Franklin Wilkins is the next step of the scientific method to predict based on the model of the X-ray diffraction pattern with the experimental data to make a serious comparison. They called once again invited Wilkins. Less than two days of work, Wilkins and Franklin used X-ray analysis of the data confirmed the double helix structure of the model is correct, and has written two experiments at the same time the report published in the UK "Nature" magazine. In 1962, Watson, Crick and Wilkins received the Nobel Prize for Physiology and Medicine, and Franklin died of cancer death in 1958 have not been awarded the prize.
In the late 1930s, the Swedish scientists on the DNA to prove it is asymmetrical. After the Second World War, with the electron microscope determination of DNA's molecular diameter of about 2nm.
Double helix structure of DNA was discovered, greatly shocked the academic community, inspired by the people's minds. From then on, people immediately in order to carry out genetics as the center of a large number of molecular biology research. First of all, around the base of 4 how to encode permutation and combination can show 20 kinds of amino acids for the Center for Experimental Research. In 1967, were cracking the genetic code, DNA in the genes so as to the molecular level to be a new concept. It shows: gene DNA molecules is actually a fragment, biological control is a trait of the genetic material of the functions and structure of the units units. The unit in a number of nucleotide fragments on the order is not arbitrary, but there are implications of the order of the password. A certain structure of the DNA, can control the structure of the corresponding protein synthesis. Protein is an important component of the composition of the organisms, the organisms are the main characters to reflect the adoption of the protein. As a result, the genetic traits of control through DNA control of protein synthesis to be achieved. On this basis, one after another have had a genetic engineering, enzyme engineering, fermentation engineering, protein engineering, the development of biotechnology is bound to make use of the law for the benefit of mankind. The development of modern biology, the more it will show up to take the lead for the subjects.
As early as 1868, people have been found in nucleic acids. Chemists in Germany Hoppe Sailor's lab, a graduate of the Swiss(1844 - 1895), his lab near a hospital threw the bandage with blood of the very sense of Interest, because he knows that those blood to defend human health, germs and "combat" and was killed in action and kill white blood cells of the human body "remains." He carefully put a bandage on the blood collected and used for decomposition of pepsin, and found the bodies of most of the cells break down, but on the nuclear non-functional. He further on the nuclear material within an analysis and found that the nucleus contains a phosphorus and nitrogen-rich material. Hoppe sail with yeast experiments to prove that the material inside the nucleus of the Mitchell findings are correct. He would like to give this separate from the nuclear material is known as "nuclide", was later found that it was acidic, so to be called "nucleic acid." Since then, people have carried out a series of effective nucleic acid.
In the early 20th century, Germany Ke Saier (1853 - 1927) and two of his students Jones (1865 - 1935) and Levin (1869 - 1940) study, understand the basic chemical structure of nucleic acids, it Is composed of a number of nucleotide molecules. By nucleotide base pairs, consisting of phosphate and ribose. There are 4 kinds of bases in which (Yin cast a glance gland, Yin guanine, thymine and cytosine), there are two ribose (ribose, deoxyribose), the nucleic acids into RNA (RNA) and deoxyribonucleic acid (DNA) .
Levin made his rush to the results of research, mistakenly believe that 4 in the nucleic acid bases in the volume is equal, so as to derive the basic structure of nucleic acids by 4 with different nucleotide bases to connect into a four-nucleoside Acid as a basis for nucleic acid into a polymer, a "four-nucleotide hypothesis." This hypothesis wrong, understanding of the complex structure of nucleic acids from the considerable obstacles, to a certain extent affected the people's understanding of the functions of nucleic acids. It is believed that although the nucleic acid present in the structure of the important - nuclear, but its structure is too simple, it is hard to imagine in the process of genetic What role.
Protein nucleic acid than found as early as 30 years, has developed rapidly. Of the 20th century, composed of 20 amino acid protein has been found to be 12, 1940, the whole was found.
In 1902, a German chemist Xie Erti charges between amino acid peptide chain link and the theory of the formation of proteins, in 1917, he was synthesized by the glycine-15 leucine and 3 of the 18 components of long-chain . As a result, some scientists the idea, is likely to be genetic in the protein plays a major role. If the nucleic acids involved in genetic, protein and must be linked to the role of the protein. As a result, at that time generally tend to think that biological protein is the carrier of genetic information.
In 1928, American scientists Griffith (1877 - 1941) with a capsule, and a strong toxic-free capsule, low toxicity of the pneumococcus experiments on rats. To have He pods high temperature to kill bacteria with no along with pods of live bacteria were injected mice, he found that the incidence of death soon rats, mice at the same time he's in the blood of the isolated bacteria living there pod. This shows that even without passing bacteria from the dead bacteria in the pod have access to what material to make a risk-free bacteria into bacteria have a pod. Assuming that the right thing to do? Griffith in a test tube experiment and found the dead bacteria with the United States are living without passing on the bacteria test tube train at the same time, without passing all the bacteria have become a pod bacteria and found so that no bacteria long pod A protein of the scare is there a risk of dead bacteria in the shell left over from the nucleic acid (as in heating, the pod of nucleic acid has not been damaged). Griffith said the nucleic acid as a "conversion factor."
In 1944, the United States Avery bacteriologist (1877 - 1955) from the United States and bacteria have been isolated activity of the "conversion factor", and that such material did a test of the existence of protein test, the results were negative, and to prove "Conversion factor" is the DNA. But this has not been found in a wide range of recognition, it is not suspected at the time of the technology in addition to net protein, the protein residues into play.
German-American scientists Delbruck (1906 - 1981) of phage group has a firm belief that Avery's discovery. Because they observed under the electron microscope of the phage into the shape and growth of E. coli. Phage bacterial cell is a host for the virus, individual small, with only the electron microscope to see it. It is like a small tadpole, the external components of the protein by the end of the first film and the sheath, the head of the internal contain DNA, the end of the end of silk sheath there, the substrate and the small hook. When the phage infection of E. coli, the tail end of the first bar in the bacterial cell membrane, and then it will be all the body's DNA were injected into bacteria cells, the protein shell remain in the bacterial cell outside, not from what the role of the . After the bacteria enter the cells of the phage DNA, on the use of bacterial material and rapid synthesis of the phage DNA and proteins, so many copy of the original size of the display exactly the same shape of a new phage until the bacteria were completely disintegrated, leaving only those phage dead bacteria , And then infect other bacteria.
In 1952, key members of the phage group Hershey (a 1908) and his students use the Chase advanced isotope labeling, so the E. coli bacteriophage experimental infection. He coli T2 phage DNA markers on 32P, the protein shell markings on 35S. Marking the first use of phage T2 E. coli infection, and then be separated from the results of the phage will be marked with 35S shell out to stay in E. coli, only the internal display with a 32P labeled nucleic acid were injected all the E. coli and E. coli within Phage successful breeding. The DNA test to prove there is transmission of genetic information of the functions of proteins and DNA by the synthesis of the directive. The result was immediately accepted by the academic community.
Almost at the same time, Austria biochemist Chargaff (1905 -) of the nucleic acid bases in 4 of the content of the outcome of the re-determination has been made. Avery in the work, if he thought the different species is due to the different DNA, the DNA structure must be very complicated, or difficult to adapt to biological diversity. As a result, he was out of the text "four nucleotide hypothesis," have had a doubt. In the 1948 - 1952 4 years, he made use of Levin times more than the precision of paper chromatography separation of 4 base pairs, with UV absorption spectra to do quantitative analysis, after repeated the experiment many times, and finally arrive at a different Levine. The results show that DNA molecules in purine and pyrimidine equal to the total number of elements, of which purine A gland and an equal number of T thymine, guanine and cytosine G Yin C equal to the number. Description of the DNA molecule A base with T, G and C is the existence of the match, which negates the "four nucleotide hypothesis", as well as to explore the molecular structure of DNA provides an important clue and based on.
April 25, 1953, the United Kingdom's "Nature" magazine published in the United States of Watson and Crick of the British University of Cambridge in cooperation with the results of research: DNA double helix model of the molecule, known as the outcome of the later 20 Century biology's greatest discoveries marked the birth of molecular biology.
Watson (1928 A) in middle school is an extremely intelligent children, 15-year-old when they entered the study at the University of Chicago. At that time, because of a person to allow an earlier study of the experimental sex education programs so that Watson had the opportunity to complete all aspects from the study of biological science courses. At the university, although Watson in genetics have little formal training, but since reading the Schrodinger's "What is life? - The physical appearance of living cells, "which prompted him to" find the genetic secrets. " He was good at brainstorming to win many long, good at using other people's ideas to enrich themselves. As long as there are convenient, do not have to force yourself to a whole new field of study, can be required knowledge. 22-year-old Watson made a doctorate, and then was sent to Europe to pursue post-doctoral researcher. In order to fully understand a gene's chemical structure of the virus, he went to study chemical laboratory in Copenhagen, Denmark. On one occasion he went to Naples, Italy, tutor to take part in a meeting of biological macromolecules, have the opportunity to listen to the British biologist physical Wilkins (1916 -) speech, Wilkins saw the DNAX-ray diffraction photograph. Since then, to find the key to unlock the structure of DNA in Watson's idea in the minds of the return. What can learn X-ray diffraction analysis of this map? So he went to Britain to study at the University of Cambridge Cavendish Laboratory, during which Watson understanding of the creek.
Crick (1916-2004) when high school passion for science, and in 1937 graduated from the University of London. In 1946, he read "What is life? - The physical appearance of living cells ", is determined to use the knowledge of physics to the study of biology, from biology to the interest. In 1947 he re-started the post-graduate study, in 1949, he Perutz used in conjunction with the X-ray study of the technical structure of the protein molecule, so this has been met with Watson. Watson, Crick was more than 12-year-old major, has not yet obtained a doctoral degree. However, very speculative to talk about them, Watson here are actually able to find how a protein is more important than DNA, is Sanshengyouxing. At the same time, Watson was in contact with his people, the creek is one of the most intelligent. They talked every day for at least a few hours to discuss academic issues. The two were complementary with each other to criticize each other, as well as stimulate each other's inspiration. They do not think the answer is to open the molecular structure of DNA genetic key to the mystery. With only the precise X-ray diffraction data in order to more quickly identify the structure of DNA. In order to get DNAX-ray diffraction, Crick invited Wilkins to come to Cambridge for the weekend. In the conversation Wilkins accepted the spiral structure of DNA point of view, but also his partner Franklin (1920-1958, F), as well as lab scientists also have been thinking very hard with the problem of DNA structure model . From from November 1951 to April 1953 for 18 months, Watson, Crick and Wilkins and Franklin are among several important academic exchanges.
In November 1951, after listening to Franklin Watson on the structure of the DNA of a more detailed report, inspired by a certain knowledge of the crystal structure analysis of Watson and Crick realized that in order to quickly establish the structure of DNA model, only Be able to use other people's analysis of the data. They quickly made a three-helical structure of DNA idea. By the end of 1951, they invited Wilkins and Franklin to discuss this model, Franklin pointed out that the water content of their DNA to less than half do so for the first time to set up the model failed.
One day, Watson went to King's College laboratory Wilkins, Wilkins Franklin recently beat out a system of "B-" DNA of the X-ray diffraction photograph. Watson saw pictures of them at once exciting, heart rate has accelerated, such as images than ever before to be the "A" is much more simple, as long as a little look at the "B-" X-ray diffraction photograph, and then by a simple calculation, Will be able to determine the number of DNA molecules in the number of nucleotide chains.
Please help Crick mathematician calculated results show that the source has attracted Yin Fu. According to their results from the Chargaff and got the two nucleic acid purine and pyrimidine two 22 equal As a result, the formation of the concept of base pairs.
They desperately to think of the 4 base sequence, time and again drawing on paper-base structure, playing with the model, repeatedly made the assumption that time and again to overthrow their own assumptions.
Watson (left) and there is a creek, according to Watson in the idea of playing with their own model, he shifted base to search for the removal of all kinds of matching. Suddenly, he found two hydrogen bonds linking the gland Yin-fat thymine and went so far as to the hydrogen bond of 3-connected guanine cytosine-Yin of have the same shape, so it boosted the spirit. Because the number of purine and pyrimidine why the number should be exactly the same as the mystery solved. Chargaff all of a sudden it became the law of DNA double helix structure of the inevitable result of the. As a result, how the chain as a template synthesis of another complementary sequence of bases is not hard to imagine the chain. In that case, the skeleton of the two chains must have the opposite direction.
After Watson and Crick tension in a row, quickly completed a metal model of DNA assembly. From this model to see, DNA from the two components of nucleotide chains, which along with the central axis of intertwined with each other in the opposite direction, much like a spiral staircase handrails on both sides is more than 2 nucleotide chains P-glycoprotein gene combined with the turn of the skeleton, and the pedal base is right. In the absence of accurate information on X-ray, they dare not conclude that the model is entirely correct.
Franklin Wilkins is the next step of the scientific method to predict based on the model of the X-ray diffraction pattern with the experimental data to make a serious comparison. They called once again invited Wilkins. Less than two days of work, Wilkins and Franklin used X-ray analysis of the data confirmed the double helix structure of the model is correct, and has written two experiments at the same time the report published in the UK "Nature" magazine. In 1962, Watson, Crick and Wilkins received the Nobel Prize for Physiology and Medicine, and Franklin died of cancer death in 1958 have not been awarded the prize.
In the late 1930s, the Swedish scientists on the DNA to prove it is asymmetrical. After the Second World War, with the electron microscope determination of DNA's molecular diameter of about 2nm.
Double helix structure of DNA was discovered, greatly shocked the academic community, inspired by the people's minds. From then on, people immediately in order to carry out genetics as the center of a large number of molecular biology research. First of all, around the base of 4 how to encode permutation and combination can show 20 kinds of amino acids for the Center for Experimental Research. In 1967, were cracking the genetic code, DNA in the genes so as to the molecular level to be a new concept. It shows: gene DNA molecules is actually a fragment, biological control is a trait of the genetic material of the functions and structure of the units units. The unit in a number of nucleotide fragments on the order is not arbitrary, but there are implications of the order of the password. A certain structure of the DNA, can control the structure of the corresponding protein synthesis. Protein is an important component of the composition of the organisms, the organisms are the main characters to reflect the adoption of the protein. As a result, the genetic traits of control through DNA control of protein synthesis to be achieved. On this basis, one after another have had a genetic engineering, enzyme engineering, fermentation engineering, protein engineering, the development of biotechnology is bound to make use of the law for the benefit of mankind. The development of modern biology, the more it will show up to take the lead for the subjects.
Distribution and function of DNA
Prokaryotic cell chromosome is a long DNA molecule. Eukaryotic cell nucleus in more than one chromosome in each chromosome with only a DNA molecule. But they are generally better than the original nuclear DNA of cells and large molecules and proteins together. The DNA molecule is a function of storing all of the species decided to RNA and protein structure of all the genetic information; planning are the order of biological cells and tissues and synthetic components of time and space; determine the biological life cycle from beginning to end and determine the biological activity of personality. In addition to the chromosomal DNA, a small number of very different structure of the DNA present in the eukaryotic cell's mitochondria and chloroplasts. DNA is the genetic material of the virus DNA.
Edit this paragraph DNA replication
DNA is the carrier of genetic information, the parental DNA molecule itself to be a template for the accurate reproduction into two copies, and assigned to the two daughter cells go in, the carrier of genetic information to complete its mission. The double-stranded DNA structure to maintain the stability of this type of genetic material and the accuracy of reproduction are extremely important.
(A) DNA replication and a half of the
Click and Waston made in the DNA double helix structure of DNA to replicate the model during the course of research conducted and found that the process of DNA replication in the base of the hydrogen bonds between the first fracture (through the helicase), the double helix structure of the helicase separating Chain were the template for synthesis of the new chain. As the offspring of each of the DNA chain from a parent and the other is a new synthesis, so-called reservations and a half to copy (semiconservative replication).
(B) DNA replication
1. Double helix of DNA helicase
(1) single-stranded DNA binding protein (single-stranded DNA binding protein, ssbDNA protein)
(2) DNA helicase (DNA helicase)
(3) DNA chain solution
2. Okazaki fragments and the semi-discontinuous replication
3. Copy and lead to the termination of the
(C) telomeres and telomerase
American Indians in 1941 McClintock (Mc Clintock) put on the telomere (telomere) of the hypothesis that there is the inevitable end of the chromosome of a special structure - telomere. Now the role of telomeres of chromosomes are known to have at least two: ① to protect against injury at the end of chromosomes, so that the chromosome remained stable; ② connected with the nuclear lamina, so that the chromosome can be positioning.
(A) DNA replication and a half of the
Click and Waston made in the DNA double helix structure of DNA to replicate the model during the course of research conducted and found that the process of DNA replication in the base of the hydrogen bonds between the first fracture (through the helicase), the double helix structure of the helicase separating Chain were the template for synthesis of the new chain. As the offspring of each of the DNA chain from a parent and the other is a new synthesis, so-called reservations and a half to copy (semiconservative replication).
(B) DNA replication
1. Double helix of DNA helicase
(1) single-stranded DNA binding protein (single-stranded DNA binding protein, ssbDNA protein)
(2) DNA helicase (DNA helicase)
(3) DNA chain solution
2. Okazaki fragments and the semi-discontinuous replication
3. Copy and lead to the termination of the
(C) telomeres and telomerase
American Indians in 1941 McClintock (Mc Clintock) put on the telomere (telomere) of the hypothesis that there is the inevitable end of the chromosome of a special structure - telomere. Now the role of telomeres of chromosomes are known to have at least two: ① to protect against injury at the end of chromosomes, so that the chromosome remained stable; ② connected with the nuclear lamina, so that the chromosome can be positioning.
The secrets of DNA
When the gene and found that the correlation between the DNA, people still want to know how the DNA is a kind of thing, it is no concrete way of life to so many messages to the new successor of it?
First of all, people want to know what DNA is composed of human love is always asked at the end of this plane. The results have called the Levin scientists through research, found that DNA from four of the smaller things, the four things named nucleotide of the total, as the four brothers, all of which nucleotide surname, But the name is different, namely, adenine (A), guanine (G), cytosine (C) and thymine (T), it is difficult to remember the names of the four, but keep in mind that as long as the DNA from four Nucleotide just get together and connect them to each other's no law, but in fact not the same nucleotide, and their combination with each other's ever-changing ways, a great mystery.
Now, people basically have to understand the genetic How did it happen. The 20th century, the study found that biology: the body is posed by the cell, the cell membrane, such as the composition of the nucleus and cytoplasm. Known in the nucleus of a material called chromosomes, which is called by some of the DNA (DNA) of the composition of the material.
Biological genetic material present in all cells, the substance called nucleic acid. Nucleic acid from the nucleotide polymerization. And each of the nucleotide phosphate, ribose and constitutes a base. There are five bases, respectively, adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). Each contains only five nucleotide base pairs in a.
The single nucleotide even as a chain, the two nucleotide chains according to a certain degree of order, and then twisted into a "cannabis"-like, it constitutes a DNA (DNA) of the molecular structure. In this structure, each of the three bases to the genetic composition of a "password" and a DNA base pairs on as many as several million, so each of the DNA is a much of the genetic code, which the possession of genetic information A countless number of such molecules on the DNA present in the chromosomes in the nucleus. As they passed cell division genetic code.
Human genetic trait passed by the password. There were about 25,000 genes, each gene is determined by the password. Human gene in both parts of the same, but different. A different part of the decision of the distinction between human beings, that is, the diversity of people. A total of DNA's genetic code 3,000,000,000, the composition of the order of about 25,000 genes.
First of all, people want to know what DNA is composed of human love is always asked at the end of this plane. The results have called the Levin scientists through research, found that DNA from four of the smaller things, the four things named nucleotide of the total, as the four brothers, all of which nucleotide surname, But the name is different, namely, adenine (A), guanine (G), cytosine (C) and thymine (T), it is difficult to remember the names of the four, but keep in mind that as long as the DNA from four Nucleotide just get together and connect them to each other's no law, but in fact not the same nucleotide, and their combination with each other's ever-changing ways, a great mystery.
Now, people basically have to understand the genetic How did it happen. The 20th century, the study found that biology: the body is posed by the cell, the cell membrane, such as the composition of the nucleus and cytoplasm. Known in the nucleus of a material called chromosomes, which is called by some of the DNA (DNA) of the composition of the material.
Biological genetic material present in all cells, the substance called nucleic acid. Nucleic acid from the nucleotide polymerization. And each of the nucleotide phosphate, ribose and constitutes a base. There are five bases, respectively, adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). Each contains only five nucleotide base pairs in a.
The single nucleotide even as a chain, the two nucleotide chains according to a certain degree of order, and then twisted into a "cannabis"-like, it constitutes a DNA (DNA) of the molecular structure. In this structure, each of the three bases to the genetic composition of a "password" and a DNA base pairs on as many as several million, so each of the DNA is a much of the genetic code, which the possession of genetic information A countless number of such molecules on the DNA present in the chromosomes in the nucleus. As they passed cell division genetic code.
Human genetic trait passed by the password. There were about 25,000 genes, each gene is determined by the password. Human gene in both parts of the same, but different. A different part of the decision of the distinction between human beings, that is, the diversity of people. A total of DNA's genetic code 3,000,000,000, the composition of the order of about 25,000 genes.
About DNA
Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. The main role of DNA is the lon-term storage of information and it is often compared to a set of blueprints, since DNA contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
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