Question

In human DNA, if adenine makes up approximately 30.9% of the bases, and guanine makes up approximately 19.9% of the bases, what will be the percentage of thymine and cytosine?

• A. 19.8% T and 19.8% C
• B. 19.8% T and 29.4% C
• C. 29.4% T and 19.8% C
• D. 29.8% T and 29.8% C
• E. 19.9% T and 30.9% C

Answer 1

Answer: (C)

29.4% T and 19.8% C

According to Chargaff’s rule, all cellular DNAs, regardless of the species, a number of adenosine residues are equal to a number of thymidine residues which means that A=T; and the number of guanosine residues is equal to the number of cytidine residues; G= C. According to the question, A and G make 30.9 and 19.9% of bases respectively, so the percentage of T and C will be 29.4 and 19.8 respectively (making the total value of bases 100).
So, the correct answer is option C.