Question

In sea urchin DNA,which is double stranded, 17% of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this DNA are:

• A. G 8.5%, A 50%, T 24.5%
• B. G 34%, A 24.5%, T 24.5%
• C. G 17%, A 16.5%, T 32.5%
• D. G 17%, A 33%, T 33%

Answer 1

The correct option is D

G 17%, A 33%, T 33%

According to Chargaff’s rule, the amount of purine is always equal to the amount pyramidines.

[A] = [T] , [G] = [C], [A] + [G] = [C] + [T]

Therefore [G] = 17%, [A] = [T] = 33%