Question

For double-stranded DNA which of the following base ratios ALWAYS equals 1?

a) (A+T)/(C+G)
b) (A+G)/(C+T)
c) (G+T)/(A+C)
d) two of the above
e) all of the above

Answer 1

The correct base ratio in double-stranded DNA that always equals 1 due to complementary base pairing is neither of the options provided but instead is the ratio of A to T and G to C. Chargaff's rules and the structure of the DNA helix support this fact.

Step-by-step explanation:

For double-stranded DNA, the base ratio that ALWAYS equals 1 is none of the options provided. Instead, the ratios of adenine (A) to thymine (T) and guanine (G) to cytosine (C) are always equal to 1 due to complementary base pairing, which is a fundamental characteristic of the DNA double helix. Chargaff's rules dictate that in any double-stranded DNA molecule, the number of A bases is equal to the number of T bases, and the number of G bases is equal to the number of C bases.

This base-pairing is explained by the fact that adenine forms hydrogen bonds with thymine, and guanine forms hydrogen bonds with cytosine, making them complementary base pairs. The options provided in the question are incorrect, as none of them represent the strict base-pairing rules that apply to the DNA structure.