Question

The short DNA segment has 80 thymine and 90 guanine bases. The total number of nucleotides are

• A. 160
• B. 40
• C. 80
• D. 340

Answer 1

The correct option is D 340

• According to Chargaff's rules in a double-stranded DNA, a number of adenine units is equal to the number of thymine units and the number of guanine units is equal to the number of cytosine units. Therefore, in the given question the number of thymine bases is 80. Thus, as per the rule stated a number of adenine bases should also be 80.
• Similarly, if the number of guanine bases is given as 90, then the number of cytosine bases should also 90 according to the Chargaff's rule. Thus, after adding the number of all bases (adenine, guanine-cytosine and thymine, i.e., 80+90+90+80). That equals 340.

So the correct answer is option D.