Complementary base pairing is the specific pairing of nitrogenous bases in DNA (and RNA) where each base on one strand forms hydrogen bonds with a matching base on the opposite strand.
In DNA:
- Adenine (A) pairs with Thymine (T)
- Guanine (G) pairs with Cytosine (C)
In RNA (where thymine is replaced by uracil):
- Adenine (A) pairs with Uracil (U)
- Guanine (G) pairs with Cytosine (C)
Key Points:
- These pairings are called complementary because the bases fit together like puzzle pieces through hydrogen bonds.
- This ensures that the two strands of DNA are complementary, not identical — if one strand has the sequence A–T–G–C, the other will be T–A–C–G.
- Complementary base pairing is crucial for:
- DNA replication – ensures accurate copying of genetic information.
- Transcription – helps form a complementary RNA strand from a DNA template.
In short:
Complementary base pairing is the rule that ensures each base bonds only with its specific partner, maintaining the structure and fidelity of genetic information.