DNA( Deoxyribonucleicacid) is a nucleic acid that contain genetic instruction and information to develop and functioning in living organisms except RNA viruses which contain RNA as genetic material. DNA play the main role of long-term information storage. Eukaryotic organisms for example animals and various kinds of plants store their most of their DNA in the nucleus and some of it in other organelles while the prokaryotic organisms such as bacteria and archaea store their DNA mainly in the cyctoplasm. The structure of the double stranded DNA was discovered by James D. Watson and Francis Crick and they found that the two helical chains of repeating units, nucleotides are each coiled round the same axis.
These two long strands entwine like vines in the shape of a double helix and the nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together. Furthermore, there is also a base which interacts with the other DNA strand in the helix. The four bases found in DNA are adenine (abbreviated as A), cytosine (C), guanine (G) and thymine (T).
Each type of base on one strand forms a bond with just one type of base on the other strand. This is called complementary base pairing. Purines form H (hygrogen) bonds to pyrimidines, with A bonding only to T, and C bonding only to G. This arrangement of two nucleotides binding together across the double helix is called a base pair. As AT forming two hydrogen bonds, GC forming three hydrogen bonds. The backbone of the DNA strand is made from alternating phosphate and sugar residues. The sugar in DNA is a pentose (5 carbon sugar).These sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand and this phenomena makes the strands as antiparallel. For more information pres here:
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