Question

If the GC content of a DNA molecule is 60%, what are the molar percentages of the four bases (G, C, T, A)?

A) G = 30%, C = 30%, T = 20%, A = 20%
B) G = 30%, C = 30%, T = 25%, A = 15%
C) G = 60%, C = 60%, T = 20%, A = 20%
D) G = 60%, C = 60%, T = 10%, A = 10%

Answer 1

The molar percentages of the four bases (G, C, T, A) in a DNA molecule with 60% GC content are: G = 30%, C = 30%, T = 20%, A = 20%.

Step-by-step explanation:

The molar percentages of the four bases (G, C, T, A) can be determined based on Chargaff's rules. According to these rules, the amount of guanine (G) is equal to the amount of cytosine (C), and the amount of adenine (A) is equal to the amount of thymine (T).

Since the GC content of the DNA molecule is 60%, this means G + C = 60%. Using Chargaff's rules, we can determine that G = 30% and C = 30%. Since G and C make up 60% of the total, the remaining 40% is divided equally between T and A. Therefore, T = 20% and A = 20%.

So the correct molar percentages for the four bases are:

• G = 30%
• C = 30%
• T = 20%
• A = 20%