Question

If a double-stranded DNA has 20% of cytosine, what will be the percentage of adenine in it?

• A. 20%
• B. 40%
• C. 30%
• D. 60%

Answer 1

The correct option is C 30%

According to Chargaff's rule, the amount of adenine is always equal to that of thymine and the amount of guanine is always equal to that of cytosine i.e., A = T and G = C. If dsDNA has 20% of cytosine, then guanine is also 20%. The remaining 60% represents both A + T molecules. Since, adenine and thymine are present in equal number, the percentage of adenine and thymine is 30% each.