Question

question 9 of 10
what is one discovery made by chargaffs team about nitrogenous bases in
dna?
a. the ratio of purines to pyrimidines is always about 1:1.

b. the four nitrogenous bases occur in equal amounts in all species.

c. pyrimidines are larger than purines.

d. the amount of adenine is always greater than the amount of
cytosine.

Explanation:

Chargaff's rules state that in DNA, the amount of adenine (A) equals thymine (T), and guanine (G) equals cytosine (C). Purines (A, G) and pyrimidines (T, C) thus have a ratio of approximately 1:1. Option B is wrong as base amounts vary by species. Option C is incorrect (purines have a double - ring structure, so they are larger than pyrimidines). Option D is wrong as A and C amounts depend on the species, and A isn't always greater than C.

Answer:

A. The ratio of purines to pyrimidines is always about 1:1.