Question

Which statement correctly describes the structure of the DNA double helix?

A. Nitrogenous bases pair with other bases in the same purine or pyrimidine groups.
B. The two DNA strands of the double helix are oriented in the same direction.
C. The amount of guanine will equal the amount of cytosine in a DNA sequence.
D. Sugar-phosphate backbones form the interior of the double helix.

Answer 1

c. The correct description of the DNA double helix structure is that the amount of guanine equals the amount of cytosine. The sugar-phosphate backbones form the exterior of the DNA helix with purine-pyrimidine base pairing inside, and the strands are antiparallel.

Step-by-step explanation:

The correct statement describing the structure of the DNA double helix is: C. The amount of guanine will equal the amount of cytosine in a DNA sequence. This refers to Chargaff's rules, which also indicate that the amount of adenine equals the amount of thymine.

The sugar-phosphate backbone forms the exterior sides of the DNA double helix, with the nitrogenous bases pairing in the interior. Base pairing occurs between a purine and pyrimidine; specifically, adenine (a purine) pairs with thymine (a pyrimidine), and guanine (a purine) pairs with cytosine (a pyrimidine).

It's important to note that the two DNA strands are antiparallel, meaning they run in opposite directions (3' to 5' and 5' to 3').