How many hydrogen bonds are present between adenine and thymine?

DNA STRUCTURE

Read the following passage carefully and answer the given questions.

DNA is a long polymer of deoxyribonucleotides. A nucleotide has three components – a nitrogenous base, a pentose sugar, and a phosphate group. There are two types of nitrogenous bases – Purines and Pyrimidines. DNA is made of two polynucleotide chains, where the backbone is constituted by sugar-phosphate, and the bases project inside. The bases in two strands are paired through hydrogen bond forming base pairs. As a result, always a purine comes opposite to a pyrimidine. This generates approximately uniform distance between the two strands of the helix. The plane of one base pair stacks over the other in double helix. This, in addition to H-bonds, confers stability of the helical structure. The two polynucleotide chains are coiled in a right-handed fashion. In eukaryotes, the DNA organisation is much more complex. There is a set of positively charged, basic proteins called histones. A protein acquires charge depending upon the abundance of amino acids residues with charged side chains.