MCQ practice · SSC Biology Board questions · Chapter 12: Heredity in Organisms and Biological Evolution
Between which two bases are there three hydrogen bonds?
Think it through first, then pick an option.
- a Adenine and thymine
- b Adenine and uracil
- c Thymine and guanine
- d Cytosine and guanine
Answer and explanation
Correct answer: d Cytosine and guanine
Guanine (G) and cytosine (C) are joined by three hydrogen bonds (G≡C).
Why the other options are wrong
- a Adenine and thymine: Adenine and thymine are joined by two hydrogen bonds.
- b Adenine and uracil: Adenine and uracil have two bonds, and uracil is not even in DNA.
- c Thymine and guanine: Thymine and guanine do not pair; thymine pairs with adenine.
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