What would you predict the %C (cytosine) to be based on this information? During your summer job at Virotech, you isolate a previously unknown virus. Analysis of its genome reveals that it is composed of a double stranded DNA molecule containing 14% T (thymine).
The correct answer to this question is 36%. In a situation like this with a double-stranded DNA, we know G (guanine) is always complementary with C (cytosine) and A (adenine) is always complementary with T (thymine).
Therefore, the percentage of G has to equal the percentage of C, and the percentage of A has to equal the percentage of T. If G=14% then C=14%, totalling 28%. Therefore A+T = 72% (the remaining out of 100%), and we know A has to equal T so we can divide 72% in half to obtain the equal parts A (36%) and T (36%).