Question

An animal cell contains 30% adenine in its nuclear DNA. What will be the percentage of cytosine in it?

• A. 20
• B. 40
• C. 50
• D. 60

Answer 1

The correct option is A 20

According to Chargaff’s rule, the amount of adenine residue is proportional to the amount of thymine. So, if adenine is 30%, thymine is also 30%. Adenine and thymine are 60% of the total nucleotides. So, the remaining 40% of nucleotides are cytosine and guanine. As the amount of guanine residue is equal to the amount of cytosine residue, so percentage of cytosine is 20%.