Question

Read the given statements carefully and select the correct one:

o in DNA, the two strands of polynucleotides are parallel to each other.
o the backbone is formed by the sugar, phosphate, sugar chain.
o the nitrogen bases are projected more or less perpendicular to the backbone but face outside.
o t and c of one strand complementarily base pairs with g and a in the other strand, respectively.

Answer 1

The correct structure of DNA involves anti-parallel strands with a sugar-phosphate backbone, where the nitrogenous bases face inward, and A pairs with T, and C pairs with G.

Step-by-step explanation:

In assessing the structure of DNA, we can identify several key characteristics based on the correct statement among the options provided. In DNA, the two strands of polynucleotides are not parallel, but anti-parallel. This means the 3' end of one strand faces the 5' end of the other strand. The backbone of DNA is indeed formed by the sugar and phosphate molecules, creating a sugar-phosphate-sugar chain.

The nitrogenous bases, which include adenine (A), thymine (T), cytosine (C), and guanine (G), are oriented perpendicular to this backbone and face inward, rather than outward, towards each other. As for the pairing of the nitrogenous bases, it's always A pairing with T and C pairing with G, which is due to their ability to form hydrogen bonds in a complementary manner, with A and T forming two hydrogen bonds and C and G forming three hydrogen bonds.