Watson-Crick pairs

Watson-Crick base pairs refer to the pariring of Nucleotide bases within DNA. There are two forms of nucleotide, a purine and a pyrimidine. Purines include Adenine and Guanine, while pyrmidines are Thymine and Cytosine. In DNA an Adenine always bonds with a Thymine, whilst Cytosine always bonds to Guanine. These bonds are hydrogen bonds. It is this type of base pairing that is important for the specificity of amino acids and in general the DNA structure. (Beckeret al.,

References:

[Becker., Kleinsmith., Hardin and Bertoni (2009) The World of the Cell, Seventh Edition, San Francisco: Pearson Education.]