Question

Choose the correct answers from the alternatives given :
The double-helix model of DNA resembles a twisted ladder in which the rungs of the ladder are

• A. sugar-phosphate paired with sugar-phosphate
• B. A paired with T and C paired with G
• C. a purine paired with a pyrimidine
• D. both (b) and (c)

Answer 1

The correct option is D both (b) and (c)

The double helix model of DNA is made of sugar-phosphate backbone. The rungs of the ladder depict the hydrogen bonds present between the base pairs. The sugar molecule of one nucleotide joins with the phosphate molecule of another nucleotide through phosphodiester bonds. There are two types of nitrogenous bases: purines (adenine and guanine) and pyrimidines (cytosine and thymine). During base pairing, purines always make bonds with pyrimidines. Adenine binds with thymine by double hydrogen bonds, while guanine binds with cytosine using triple hydrogen bonds.

So, the correct option is 'both (b) and (c)'.