Here's a breakdown:
* Adenine (A) always pairs with Thymine (T). They form two hydrogen bonds.
* Guanine (G) always pairs with Cytosine (C). They form three hydrogen bonds.
This specific pairing is known as complementary base pairing and is essential for:
* DNA replication: When DNA replicates, the two strands separate, and each strand acts as a template for the synthesis of a new complementary strand.
* Protein synthesis: DNA's sequence of nitrogen bases dictates the sequence of amino acids in proteins.
Here's a visual representation:
* A-T pair:
* Adenine's amino group forms a hydrogen bond with thymine's carbonyl group.
* Adenine's nitrogen atom forms a hydrogen bond with thymine's nitrogen atom.
* G-C pair:
* Guanine's amino group forms a hydrogen bond with cytosine's carbonyl group.
* Guanine's nitrogen atom forms a hydrogen bond with cytosine's nitrogen atom.
* Guanine's carbonyl group forms a hydrogen bond with cytosine's amino group.
The three hydrogen bonds between G and C are stronger than the two hydrogen bonds between A and T. This contributes to the overall stability of DNA.
In summary:
* Nitrogen bases bond through hydrogen bonds.
* Adenine pairs with thymine (A-T), forming two hydrogen bonds.
* Guanine pairs with cytosine (G-C), forming three hydrogen bonds.
* This complementary base pairing is essential for DNA replication and protein synthesis.
