base pair

combination of 2 nucleotides (A and T or G and C) held together by weak hydrogen bonds; the DNA double helix is formed when a base pair of nucleotides in the DNA strands are connected by these bonds.

(Abbreviation: bp). The two separate strands of a nucleic acid double helix are held together by specific hydrogen bonding between a purine and a pyrimidine, one from each strand. The base A pairs with T in DNA (with U in RNA ); while G pairs with C in both DNA and RNA. The length of a nucleic acid molecule is often given in terms of the number of base pairs it contains.

Two bases which form a "rung of the DNA ladder." A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a base. The bases are the "letters" that spell out the genetic code. In DNA, the code letters are A, T, G, and C, which stand for the chemicals adenine, thymine, guanine, and cytosine, respectively. In base pairing, adenine always pairs with thymine, and guanine always pairs with cytosine. See also nucleotide