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 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.