WATSON AND CRICK'S MODEL OF DNA

WATSON AND CRICK'S MODEL OF DNA 

Watson and crick in 1953 discovered the structure of DNA by the method of x-ray diffraction and received nobel prize for this work.



Points of DNA :


1.DNA is composed of two strands
2.Both the strands are helically coiled and antiparallel
3Tthe strands are composed of nucleotides.therefore DNA strands are polynucleotide chains
4.A DNA nucleotide is composed of three types of moeioties.they are deoxyribose sugar,nitrogen base and      phosphate.
5.One strand of a DNA runs in 3'-5' direction,whereas other runs in 5'-3' direction.
6.The strands are linked together by weak hydrogen bonds formed between nitrogen bases of nucleotides
7.In one strand,there may be any sequence of nitrogen bases but in another there must be complementary          bases i.e A with T or G with C and vice versa.
8.Adenine binds with thymine and viceversa with double hydrogen bonds.
9.Guanine binds with cytosine with triple hydrogen bonds.
10.The number of purine bases are equal to number of pyrimidine bases.
11.Length of one complete turn is 34 * 10^-10 m
12.Width of DNA is 20* 10^-10 m
13.There are only 10 base pairs in one complete turn.
14.Distance between two nitrogen bases in DNA is  10^-10 m


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