Deoxyribonucleic acid (DNA)


Avery and his associates first suggested that genetic material was carried in nucleic acids which had just been discovered in the 1940s. These were acids found only in the nucleus hence the name nucleic acids. The acids were known to be of two types- deoxyribonucleic acids (DNA) and ribonucleic acids (RNA). This ended the previously theory which had suggested that genes were carried in proteins.  The structure of the DNA and the way and manner by which it replicates itself just as the chromosomes in which it is embedded still remained a mystery until Watson and Crick  suggested the double helix model of DNA structure following the Xray studies. Modern molecular biology therefore started with Watson and Crick in 1953. They proposed the double helix model of DNA structure and also showed the backbone of the DNA to be nucleotide bases which link to each other to form a continuous chain of nucleotide bases. The bases can be either purines or pyrimidines. They are attached to a pentose sugar, and a phosphate radical. The bases pair in definite method in what is now known as hybridisation (the formation of two chains linked together by bonded purine and pyrimidine bases). Adenine pairs with thymine (A-T) while cytosine pairs with guanine (C-G). The pentose sugar can be either ribose sugar (with hydroxyl group present) or a deoxyribose sugar (with the absence of hydroxyl group).

DNA strand









Cell types

Organ integration



Chemical Pathology


Molecular biology


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