DNA consists

DNA consists of many deoxidization nucleotide sequence according to certain residue, each with 3-5 phosphate ester key of long chain connected. Most of the DNA contains two such long chain, and some results, such as DNA, e. coli X174 suits G4, phage M13 etc. Some DNA, DNA for circular for linear. Mainly contains adenine and guanine and thymine bases cytosine and four bases. In certain types of DNA methylation cytosine, 5 - in a certain extent, which replaced cytosine wheat embryo DNA methylation cytosine 5 - especially rich, up to 6 percent. Moore In some phage, 5 - n-hydroxymethyl cytosine replaced cytosine. The 1940s, hargaff guthrie E.C (that) of different species of DNA bases are different, but the number of adenine is equal to the number of thiamine (= T), guanine is equal to the number of cytosine (G = C), and number of equal to number of pyrimidines). Generally depicted in several layers structure of DNA.
The primary structure of DNA level structure is the base sequence. Gene is a segment of DNA genetic information storage, gene in its base in sequence. 1975 American gilbert W.G (UK) and the sanger ilbert F.S (anger) founded the DNA level structure of rapid determination methods, 1980 year of their chemistry prize. Since then, and constantly improve measurement method, the primary structure of DNA has many established. If people mitochondrial DNA contains a ring that 16569, lambda phage DNA contains a base pairs, rice 48502 134525 containing a base pairs chloroplasts genome, tobacco chloroplasts genome contains 155844 a base pairs, etc. Now, the United States has 10 to 15 years in human DNA molecules in about 30 billion for all nucleotide sequence of determination.
Secondary structure in 1953, Watson and Crick (Watson) Crick (.) the basic structure of DNA double helix fiber structure, then this is recognized by scientists model, and the explanation for replication, and other important transcription process of life. For the further research, humidity and base sequences that etc, DNA double helix can have many types, mainly divided into A and B and Z three categories.
Generally, the closest to the cell B configuration of DNA double helix conformation, it is very similar to model. DNA and RNA molecule - the double helix area and the formation of transcription DNA molecule hybridization RNA conformation close -. Z - DNA to nucleotide dimers for unit, the Lord left to wound is serrated (Z) chain, the name. This configuration for a nucleotide chain of purine cytosine alternate area. In 1989, the American scientists scanning tunneling microscopy method directly observed double-helix DNA double-helix DNA in 1952, Austria, African American biochemist captains E.c hargaff gadamer check (1905 -), the four determination of DNA base, the content of fat poison and found adenocarcinoma of the number of thymine bases, bird whisper fat with equal the number of cytosine. This makes Watson and crick immediately thought of four bases exist between two corresponding relationship, formed the glands and thymine * matching belt whisper, birds and cytosine matching belt whisper.