11.09.2008
DNA loop
Closed-loop DNA (closed circular DNA) no fracture of the ring double-stranded DNA, also known as the super-helix DNA. Due to their double-stranded helical structure of the closure, resulting in a further rotation of the entire DNA molecule formed by the three-tier structure of the song. In addition, if a chain of 2 or on different parts of a fracture, it will become a spin-free song of the open-loop DNA molecules. Cells extracted from the DNA plasmid or virus, there are elements of open-loop and closed loop these two elements. Both can be combined with the ability of the different pigments, and the two separated.
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.
Human Genome Project
Human Genome Project (human genome project, HGP) by the United States in 1985, scientists first proposed, in 1990, formally launched. United States, Britain, the Republic of France, the Federal Republic of Germany, Japan and Chinese scientists participate in the value of 3,000,000,000 U.S. dollars of the Human Genome Project. The plan aims to more than 30 billion base pairs constitute the human genome sequencing accuracy and found that all of the human genome and its clear position on the chromosome, deciphering the genetic information of all mankind. And the Manhattan atomic bomb program and the Apollo lunar landing program and called the three major science programs.
June 26, 2000, to participate in the Human Genome Project of the United States, Britain, the Republic of France, the Federal Republic of Germany, Japan and China's State 6, scientists announced that the draft of the human genome map has been completed. Completion of the sequencing requirements of the final map used in the cloning can be faithful to the autosomal on behalf of the genome structure, sequence error rate of less than one ten thousandth. 95% of the euchromatin region has been sequenced, each of the Gap is less than 150kb. Completion of the map will be completed in 2003, is expected to more than 2 years ahead of schedule.
Scientists in the United States and Britain on May 18, 2006 in the UK "Nature" magazine published an online version of the last of the human chromosomes - 1 gene on chromosome sequencing.
In all 22 pairs of human autosomal, chromosome 1 contains the largest number of genes, at 3141, is twice the average, a total of more than 223,000,000 base pairs are also the most difficult to decipher. A 150 United Kingdom and the United States team of scientists took 10 years to complete the sequencing of chromosome 1 of the work.
Scientists announced that more than one occasion of the Human Genome Project was completed, but the introduction of all this is not the whole, this time fixing the "book of life" is more accurate coverage of the human genome, 99.99%. Interpretation of the human genetic code the "book of life" declaration, which lasted 16 years, the Human Genome Project finished writing the last chapter.
June 26, 2000, to participate in the Human Genome Project of the United States, Britain, the Republic of France, the Federal Republic of Germany, Japan and China's State 6, scientists announced that the draft of the human genome map has been completed. Completion of the sequencing requirements of the final map used in the cloning can be faithful to the autosomal on behalf of the genome structure, sequence error rate of less than one ten thousandth. 95% of the euchromatin region has been sequenced, each of the Gap is less than 150kb. Completion of the map will be completed in 2003, is expected to more than 2 years ahead of schedule.
Scientists in the United States and Britain on May 18, 2006 in the UK "Nature" magazine published an online version of the last of the human chromosomes - 1 gene on chromosome sequencing.
In all 22 pairs of human autosomal, chromosome 1 contains the largest number of genes, at 3141, is twice the average, a total of more than 223,000,000 base pairs are also the most difficult to decipher. A 150 United Kingdom and the United States team of scientists took 10 years to complete the sequencing of chromosome 1 of the work.
Scientists announced that more than one occasion of the Human Genome Project was completed, but the introduction of all this is not the whole, this time fixing the "book of life" is more accurate coverage of the human genome, 99.99%. Interpretation of the human genetic code the "book of life" declaration, which lasted 16 years, the Human Genome Project finished writing the last chapter.
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