alleryAccording to the Watson and Crick model, the nitrogenous base adenine always pairs with which base?
AGuanine
BCytosine
CUracil
DThymine
Answer & Solution
Correct answer: D. Thymine
1. DNA base pairing is always between a purine and a pyrimidine.
2. Adenine pairs with thymine using two hydrogen bonds.
3. Cytosine pairs with guanine using three hydrogen bonds, which rules out options A and B for adenine.
4. So adenine pairs with thymine, option D.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 18 Genetics "Structure of DNA", p.274_
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