Question

What statement below explains the uniform width of the DNA molecule along its entire width?

a. A purine nitrogenous base always pairs with another purine nitrogenous base
b. A pyrimidine nitrogenous base always pairs with another pyrimidine nitrogenous base
c. A pyrimidine nitrogenous base always pairs with a purine nitrogenous base
d. Repulsion between phosphate groups keeps the strands a uniform distance apart
e. Attraction between phosphate groups keeps the strands a uniform distance apart

Answer 1

The uniform width of the DNA molecule is due to the pairing of a pyrimidine nitrogenous base with a purine nitrogenous base, which ensures a consistent width along the helical structure.

Step-by-step explanation:

The statement that explains the uniform width of the DNA molecule along its entire length is that c. A pyrimidine nitrogenous base always pairs with a purine nitrogenous base. This is due to the specific pairing of the nitrogenous bases: adenine (A) with thymine (T), and cytosine (C) with guanine (G), ensuring a consistent width.

These bases form complementary base pairs of one purine and one pyrimidine, which maintain the DNA's helical structure's constant diameter. If purines were to pair with purines, or pyrimidines with pyrimidines, the uniform width would not be maintained. The hydrogen bonds between these bases further stabilize the DNA structure, creating a consistent shape and size along the entirety of the molecule.