Question

The distance between the two strands of a dsDNA is approximately uniform because of the following reason?

Answer 1

In the complementary base pairing of DNA, the purine always pairs with a pyrimidine. As a result, Adenine pairs with thymine with two hydrogen bonds and Cytosine pairs with Guanine with three hydrogen bonds.
This generates approximately a uniform distance between the two strands of the double stranded DNA.
Hence, the correct answer is option “A” - Purine always comes opposite to pyrimidine in a dsDNA.