[Campbell Biology P.366] According to Chargaff's rules, which of the following statements is... | Practice Question
According to Chargaff's rules, which of the following statements is true regarding the base composition of DNA?
A: The percentage of adenine (A) always equals the percentage of guanine (G).
B: The base composition of DNA varies significantly between different species.
C: In any given species, the percentages of all four bases (A, T, G, C) are always exactly equal.
D: The total percentage of purines (A+G) is always different from the total percentage of pyrimidines (C+T).
Explanation
One of Chargaff's rules states that DNA base composition varies between species. For example, sea urchin DNA has 32.8% A, while E. coli DNA has 24.7% A, demonstrating species-specific variation.