DNA probe
DNA probe is the most commonly used DNA probe that several hundred base pairs in length more than double-stranded DNA or single chain DNA probe. DNA probe has been the large number, 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 should be a specific, such as bacterial virulence factor gene probes and human Alu probe. These DNA probes depends on access to the molecular cloning technology development and application. Bacteria for example, molecular hybridization technology for bacterial strain identification and classification than the percentage of the value of G + C to accurate, is a bacterial taxonomy development direction. In addition elements of the high sensitivity of hybridization, molecular hybridization in the diagnosis of clinical microbiology has broad prospects. Bacterial genome size of approximately 5 × 106bp, containing about 3,000 genes. Between the vast majority of bacterial DNA is the same, in order to get a specific nucleic acid probe bacteria, usually to build a library of bacterial genomic DNA approach will be of bacterial DNA into small fragments were cloned after the genome contains all the information Cloning library. Then use a variety of other bacteria's DNA as a probe to screen a hybridization signal Cloning been removed, the last remaining non-hybrid with any other bacterial cloning may contain the bacteria specific DNA fragment. This recombinant plasmid probe after further identification markings can be identified by DNA sequence analysis of their genetic origin and function. So to be a specific DNA probe is more often tedious. Cloning DNA probe can be applied in the screening serology, as well as the different DNA library is built for the expression of cloned colony or plaque after the release by cracking antigen expression, and then use the source of bacteria polyclonal antiserum screening positive clones , which has a number of positive clones by other bacteria to the anti-serum screening, but only with the response of serum anti-bacterial expression of this bacterial clones that contain specific gene fragment, it is the protein encoded by specific bacteria. Use this expression library by screening apparently just specific gene probe.
DNA repair
DNA repair (DNA repairing) cell DNA damage by the response, this response may resume DNA structure as it is, can re-implementation of its original function, but sometimes are not able to completely eliminate the DNA damage, but cells This tolerance to DNA damage and can continue to survive. Perhaps this has not fully repair the damage and hold down the right conditions will be shown under (such as of cancerous cells, etc.), but if the cells do not have this repair, it is impossible to deal with the frequent occurrence of DNA damage in the incident, survival . Therefore DNA repair research is to explore an important aspect of life, but also with military medicine, oncology, and other closely related. On the different DNA damage, cells can have different repair responses. DNA contains A, C, G and T four bases, under normal circumstances A - T, C - G base pairs combination of a DNA cross-linked files. Interpretation of DNA genes is through these bases in order to convey instructions to the cells, control cells work. Many factors could cause DNA strand breaks, DNA chain in the reorganization to rearrange the base, resulting in the interpretation of the original base sequences and different, send the wrong instructions, resulting in the wrong cell growth and working conditions, variation in the cell, also will have the tumor cells. Tumor cells will absorb a large amount of nutrients or normal human cells grow rapidly, tumor cells than normal cells much larger nucleus than the normal 1-5 times, and more deformed, and so on. At the same time tumor DNA chain in the same situation will be broken, because DNA repair and half with its own reservations about the function of reproduction, DNA ligase can be linked to DNA fragment again in the next rotation of the role of re-forming spiral. And a small section of genetic DNA of tumor cells can generate new characteristics of tumor cells. Now scientists are often referred to cloning, the DNA is the use of this property. So most of the tumor DNA chain reorganization is a change of two or more of a change process, which form the tumor cell replication and propagation, which resulted in tumor expansion, proliferation, transfer and deterioration, and ultimately threaten human health and life.
[DNA replication:
DNA replication is double-stranded DNA prior to cell division in the replication process, the result is copied into a double strand of the double-stranded two different (if the normal process of reproduction), with each double-strand of the double-stranded, like the original . This process is called semi-through replication mechanism to retain the smooth completion. Copy can be divided into the following phases:
Start-up phase: gyrase in local start the double helix structure of DNA molecules a single chain of primers to identify the start bit, in order to solve the section of DNA as a template, according to the 5 'to 3' direction of short-chain RNA synthesis. Forming RNA primer.
DNA fragments generated: provide a primer 3'-OH ends on the basis of DNA polymerase chain of the two catalytic DNA replication process at the same time, because the process can only be copied from the 5'-> 3 'direction synthesis, a chain to continuous synthesis, a separate chain of subparagraph, each of which became a short chain Okazaki fragment (Okazaki fragments).
RNA hydrolysis primer: When a certain length of DNA synthesis, DNA polymerase hydrolysis of RNA primer, Buchen gap.
DNA ligase DNA fragments will phosphate ester bond of linking it to a complete DNA molecule.
Finally new synthetic fragments of DNA gyrase help in the re-formation of spiral.
[Single-strand DNA]
Single-stranded DNA (single-stranded DNA) to the majority of the double helix structure of DNA exist, but the heat or alkaline treatment will be linked into a single state. Single-strand DNA refers to the existence of this state of the DNA. Single strand DNA molecules in the fluid mechanics nature, absorption spectra, base response nature of both double-stranded DNA and different. Certain phage particles containing single-chain ring of DNA, the phage DNA in the cell proliferation when a double-stranded DNA.
Closed-loop [DNA]
Closed-loop DNA (closed circular DNA) did not fracture of the double-stranded circular DNA, which is also known as super-helical DNA. Due to the double-stranded helical structure of their closure, with the result that the entire DNA molecule further spin-formed three-tier structure. If another one or two different parts of the chain have a fracture, it will become a Rotary song open-loop DNA molecule. Extracted from the cells in the plasmid or viral DNA contains the closed-loop and open-loop that two kinds of molecules. According to the two pigment can be combined with the ability of different, and both will be separated from.
DNA [link]
DNA link (Linker DNA): nuclear body, in addition to 146 bp DNA, the core of all DNA.
[Template DNA]
Template DNA can be single-chain molecule, it can also be a double-stranded molecule, it could be linear elements, it can also be a cyclic molecules (molecular ratio ring linear amplification effect of a lesser extent). On the template DNA, PCR impact The main factor is the number of templates and purity.
[Complementary DNA]
Complementary DNA (cDNA, complementary DNA) gene of a double-stranded DNA molecule with a single chain as a template, the transcription produce its sequence complementary messenger RNA molecules, and then the role of reverse transcriptase, to mRNA molecules as templates, and a Synthesis mRNA sequence complementary single strand DNA, and finally a single-stranded DNA as a template synthesis another one with the complementary single strand DNA, the two complementary single strand DNA molecules to form a double-stranded cDNA molecule. Therefore, the double-stranded cDNA sequence elements with the mRNA transcription of the gene is the same. therefore a cDNA molecule on behalf of a gene. cDNA but still different from the genes, because a gene mRNA transcription, coding some of the intron sequence that was deleted, retained only the coding sequence, that is, Exon. cDNA sequence than it should be much shorter sequence, because cDNA gene are not included in the non-coding sequences - intron.
[DNA restriction fragment length polymorphism analysis:
In the human genome, an average of about 200 pairs a base mutation can occur (known as the neutral mutations), neutral mutations lead to inter-individual differences in nucleotide sequence, known as DNA polymorphism. Many polymorphisms in DNA restriction enzyme recognition site, the enzyme DNA fragment length will be a different fragment, known as restriction fragment length polymorphism (RFLP). RFLR way by Mendelian genetics, in a particular family, and if a disease-specific gene fragment polymorphism closely linked polymorphic fragments that can be used as a kind of "genetic markers" to family members or judgement whether fetal genes that cause carriers. A hemophilia, cystic fibrosis and phenylketonuria, and other lesions can be diagnosed using this method.
Monday, April 21, 2008
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