Problem Set — DNA Base Composition (Step-by-Step Solutions)

Problem 1: A double-stranded DNA has 30% adenine. Calculate: (a) % Thymine, (b) % Guanine, (c) % Cytosine, (d) GC content.

Solution: Step 1: Apply Chargaff's rule A = T → Thymine = 30% Step 2: A + T = 30% + 30% = 60% Step 3: G + C = 100% - 60% = 40% Step 4: Since G = C → G = C = 20% Step 5: GC content = G + C = 40%

Answers: T = 30%, G = 20%, C = 20%, GC content = 40%