AP Biologymediummcq1 pt
Why is the pairing of purines with pyrimidines important for DNA structure?
A.It keeps the double helix a constant width
B.It allows DNA to dissolve in water
C.It stores energy in the helix
D.It prevents all mutations
Explanation
Core Concept
Each purine–pyrimidine pair spans the same distance, so the helix is uniform. Purine–purine pairs would bulge; pyrimidine–pyrimidine pairs would pinch.
Correct Answer
AIt keeps the double helix a constant width
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