Question

Assume that the molar percentage of thymine in a double-stranded DNA is 20%. What are the percentages of the four bases (G, C, T, A)? If the DNA is single-stranded, would you change your answer?

A) G = 20%, C = 20%, T = 20%, A = 40%; No change for single-stranded DNA.
B) G = 30%, C = 30%, T = 20%, A = 20%; Change for single-stranded DNA.
C) G = 20%, C = 20%, T = 20%, A = 40%; Change for single-stranded DNA.
D) G = 30%, C = 30%, T = 20%, A = 20%; No change for single-stranded DNA.

Answer 1

In a double-stranded DNA, the molar percentage of thymine is 20%. The percentages of the four bases in a double-stranded DNA are G = 30%, C = 30%, T = 20%, and A = 20%. In single-stranded DNA, the percentages of each base would remain the same, but the total add up to 100%.

Step-by-step explanation:

In a double-stranded DNA, the molar percentage of thymine is 20%. Since DNA base pairs follow Chargaff's rules, where A pairs with T and G pairs with C, the percentage of adenine is also 20%.

Therefore, the percentages of the four bases in a double-stranded DNA are G = 30%, C = 30%, T = 20%, and A = 20%.

If the DNA is single-stranded, the answer would change. In single-stranded DNA, the molar percentages of each base would remain the same, but the total add up to 100%. Therefore, the percentages of the four bases in single-stranded DNA would be G = 30%, C = 30%, T = 20%, and A = 20%.