Describe the structure of DNA with diagram as given by Watson and Crick.

The “specific pairing” is a key feature of the Watson and Crick model of DNA, the pairing of nucleotide subunits. The DNA is made up of two strands which is polynucleotide and run in a spiral manner and in this structure, the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine that are nitrogenous bases. A spiral turn consists of ten bases stacked at an interval of 0.34 nm and the pitch is 3.4 nm. In particular, the length of each base pair is the same and they fit equally between the two phosphate backbones. The base pairs are held together by hydrogen bond as A=T and G C. One end of the strand is called 5’ end where the fifth carbon of the pentose sugar is free and the opposite strand is called 3’ end where the third carbon of the pentose sugar isfree.