DNA is the carrier of genetic information

DNA is the carrier of genetic information, the parent must take their own DNA molecule as a template accurate reproduction into two copies, and assigned to the two daughter cells, go to complete its mission of the carrier of genetic information. And the double-stranded DNA structure of this type of genetic material for the maintenance of the stability and the accuracy of reproduction are extremely important. (A) DNA copy of the semi-reservation Click Waston and raised in the DNA double helix structure on the model of DNA replication during the process of the study, they speculate, DNA base pairs in the process of copying the hydrogen bonds between the first fracture, double helix of the Rotary separately, were linked to each template Synthesis of the new chain, each offspring of a DNA chain from the pro-generation, and the other is a new synthesis, so as to retain a half-copy (semiconservative replication). (B) DNA replication 1. DNA double helix of the rotation (1) single chain DNA-binding protein (single-stranded DNA binding protein, ssbDNA protein) (2) DNA helicase (DNA helicase) (3) DNA of the chain 2. Okazaki fragments and a half does not copy a row 3. Copy the trigger and termination (C) telomeres and telomerase 1941-American Indians McClintock (Mc Clintock) raised a telomere (telomere) of the hypothesis that the chromosome ends must exist a special structure - the telomere. Telomere now known at least two roles: ① chromosome end protection from damage to chromosomes remained stable; ② and nuclear fiber-connected so that the chromosome can be targeted. [DNA of the physical and chemical properties -- [Edit this paragraph] DNA is macromolecular polymers, DNA solution for the polymer solution, with very high viscosity. DNA on the role of ultraviolet radiation is absorbed, when the nucleic acid degeneration, the absorption value increased when the degeneration of the nucleic acid can be complex, absorption values will be restored to the original level. Temperature, organic solvents, acidity, urea, amide, and other reagents DNA molecules can cause degeneration, even in the DNA double bond between the hydrogen bond breaking double helix structure untied. DNA (deoxyribonucleic acid) that DNA (genes and chromosomes an integral part of) deoxynucleotidyl the polymer, is the major components of chromosomes. The vast majority of genetic information stored in the DNA molecule. [Distribution and function -- [Edit this paragraph] Prokaryotic cell chromosome is a long DNA molecule. Eukaryotic cells in more than one chromosome, each chromosome containing only a DNA molecule. But their general than the original cells in the DNA molecule and protein and the combination. DNA molecule's function is the storage of all species decision RNA structure of the protein and all the genetic information; orderly planning of cells and tissue components of the time and space; identified throughout the life cycle of biological activity and identify biological personality. In addition to chromosomal DNA, a very small amount of the different structure of DNA found in eukaryotic cells in the mitochondria and chloroplasts. DNA of the virus genetic material is DNA. [The discovery of DNA -- [Edit this paragraph] Since the genetic Mendel's law was re-discovered, the people also raised a question: genetic factor is not a material entity » In order to solve the problem of what is, people began to DNA and protein research. As early as 1868, people have discovered DNA. German chemist in the laboratory Huopei Siler, a Swiss post-graduate名叫米歇尔(1844 - 1895), his lab near a hospital threw the bandage with a sense of Nongxue Interest, because he knows that those Nongxue to defend human health, germs and "combat" and died in the WBC and was killed in human cells, "body." So he carefully the bandage on the Nongxue collected and used pepsin decomposition, and found the bodies of most of the cell decomposition, but the nuclear non-functional. He further material within the nucleus of an analysis and found that cells containing a phosphorus and nitrogen-rich material. Huopei Siler experiments with yeast, that the nucleus Michel substances found to be correct. So he would give such a separation from the nucleus of the material named "nuclide", and later it was discovered that it was acidic, so to call "DNA." From then on the people of nucleic acid carried out a series of fruitful research. 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 acid, that it Nucleotide is composed of many macromolecules. Nucleotide base pairs from, ribose and phosphate posed. Of which there are four kinds of bases (gland Piao Yin, the birds allopurinol-Yin, thymine and cytosine), there are two ribose (ribose, deoxyribose), the DNA into RNA (RNA) and deoxyribonucleic acid (DNA) . Levin eager to present his research results, the misconception that four kinds of bases in DNA, are equivalent to the volume, which is derived from the basic structure of DNA by four with different nucleotide base pairs of connecting the four-nucleoside Acid, as the basis for a nucleic acid polymer, proposed a "four nucleotide hypothesis." This hypothesis wrong, the understanding of the complex structure of nucleic acids from the considerable obstacles, also, to a certain extent, affected the people's understanding of the function of DNA. It was felt that although the DNA structure exists in the important - the nucleus, but its structure is too simple, it is difficult to envisage it in the process of genetic what role. Protein than the discovery of DNA as early as 30, have developed rapidly. The beginning of the 20th century, composed of 20 kinds of protein has 12 kinds of amino acids were found to 1940, all were found. 1902, a German chemist for Xie Erti between amino acid peptide chain connected to the formation of protein theory, in 1917 he was synthesized by the glycine 15 leucine and three of the 18 components of long-chain peptide . Thus, some scientists envisaged, it's likely that the genetic protein plays a major role. If the participation of genetic DNA, and protein is also bound together the nucleoprotein at work. Therefore, when biological protein is generally inclined to think that the carrier of genetic information. 1928, U.S. scientists Griffith (1877 - 1941) have used a capsule, and a toxic-free capsule, toxic weak Streptococcus pneumoniae experiments on rats. He used a high temperature to kill bacteria pod after pod with no live bacteria inject people with mice, rats and he soon found that the incidence death, and he's in the blood of rats from isolated the bacteria live in a pod. This shows that even without passing bacteria from the dead of a pod of what was in the material, so that no dioxin into a pod of bacteria. This assumption is correct? » Griffith also in the test tube experiments and found to have died in the U.S. with live bacteria without passing on the bacteria at the same time in test-tube culture, without passing all of a pod into a bacteria, and found that no pod of long Protein to dioxins is dead in a pod of shell left over from the nucleic acid (as in the heating, dioxin in the nucleic acid has not been damaged). Griffith said the DNA for "transforming factor." 1944, the United States Xijunxuejia Avery (1877 - 1955) from the United States have isolated the activity of the "conversion factor", and this kind of material to the test whether there is the protein test results were negative, and proved "Conversion factor" is the DNA. However, this discovery has not been widely recognized, people suspected of technology at that time can not be a net addition of protein, a protein residue into the role. American scientists德尔布吕克Germany (1906 - 1981) of the phage group firmly believe that the discovery of Avery inalienable. Because they are under the electron microscope to observe the shape of the phage into E. coli and the growth process. Phage bacterial cell is a host for the virus, individual and small, with only electron microscope to see it. It is like a small tadpole, the external is composed of protein from the first film and the tail sheath, the head of the internal containing DNA, on the tail end of silk sheath, the substrate and small hook. When the phage infection Escherichia coli, the first扎in the tail end of the cell membrane of bacteria, then it would inject all of the DNA in human cells to the bacteria, protein shell of bacteria cells remain on the outside, no longer what role the . After the bacteria enter the cells of the phage DNA, the use of bacterial material and rapid synthesis of DNA and protein phage, which many copy and the original shape of the same size phage new phage, until the bacteria was completely disintegrated, these phage did not leave the dead bacteria , Go the other bacterial infection. In 1952, key members of phage dna group Heer Xi (1908) and his students Chase isotope tag with advanced technology, do phage infection of the E. coli experiments. He E. coli T2 phage DNA markers on 32 P, protein shell markings on the 35 S. To use the T2 tag phage infection of the E. coli, and then be separated, the phage will be marked with 35 S shell to stay outside in E. coli, only within a 32 P phage DNA markers were all Note Escherichia coli, E. coli, and Phage the successful conduct of breeding. This experiment proved that a DNA transfer of genetic information, which is the protein from the DNA of the directive. This result was immediately accepted by the academic community. Almost at the same time, Austria biochemists Chargaff (1905 -) in the four kinds of nucleic acid bases in the re-determination have been fruitful. In Avery's work under the influence, he considered that if the different species is due to the different DNA, the DNA structure must be very complicated, or difficult to adapt to biological diversity. Therefore, he set out on the text of the "four nucleotide hypothesis" had a doubt.dna dna dna dna dna