Nucleic Acids
In the Watson–Crick double helical model of DNA, which of the following base-pair combinations and number of hydrogen bonds is CORRECT?
Select the correct option:
Solution
A–T: 2 hydrogen bonds; G–C: 3 hydrogen bonds
According to Watson and Crick's model of B-DNA, complementary base pairing occurs between Adenine (A) and Thymine (T) via 2 hydrogen bonds, and between Guanine (G) and Cytosine (C) via 3 hydrogen bonds. Because G–C pairs have one additional hydrogen bond, DNA rich in G–C content has a higher melting temperature (Tm). This stronger G–C interaction is exploited in PCR primer design — primers with higher G–C content bind more stably. The two strands run antiparallel (one 5'→3' and the other 3'→5').
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About This Question
- Subject
- chemistry
- Chapter
- biomolecules
- Topic
- nucleic acids
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
A–T: 2 hydrogen bonds; G–C: 3 hydrogen bonds
According to Watson and Crick's model of B-DNA, complementary base pairing occurs between Adenine (A) and Thymine (T) via 2 hydrogen bonds, and between Guanine (G) and Cytosine (C) via 3 hydrogen bonds. Because G–C pairs have one additional hydrogen bond, DNA rich in G–C content has a higher melting temperature (Tm). This stronger G–C interaction is exploited in PCR primer design — primers with higher G–C content bind more stably. The two strands run antiparallel (one 5'→3' and the other 3'→5').
This easy difficulty chemistry question is from the chapter biomolecules, covering the topic of nucleic acids. It appeared in the 2025 exam.
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