AP BIOLOGY

Detailed explanation-1: -Suppose a double-stranded DNA molecule was shown to have 15% adenine bases. What would be the expected percentage of guanine bases in that molecule? 35% (This is an application of Chargaff′s rule.

Detailed explanation-2: -Thus, if DNA molecule contains 15% adenine then C and G will constitute 70%, out of which guanine will be 35%.

Detailed explanation-3: -We know that the sample is 35% adenine, which tells us that it is also 35% thymine. We know that cytosine and guanine pair together and will be present in equal amounts, so we can divide this final total by 2 to find our answer. The sample is 35% adenine, 35% thymine, 15% guanine, and 15% cytosine.

Detailed explanation-4: -If a DNA sample were composed of 15% adenine then there would also be 15% thymine according to Chargaff’s rules. Chargaff’s rules explained that adenine always pairs with thymine and cytosine always pairs with guanine in a DNA molecule.

Detailed explanation-5: -The concentration of these four bases will make together 100%, that’s why in this case, 15% is Thymine, 15% is Adenine together making 30%. Remaining 70% is guanine and Cytosine pair i.e. 35% Guanine and 35% cytosine.