Base pair

In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). As DNA is usually double-stranded, the number of base pairs in the dsDNA strand equals the number of nucleotides in one of the strands. In DNA, adenine and thymine, as well as guanine and cytosine, can be a base pair. In RNA, thymine is replaced by uracil.

Related Topics:
Molecular biology - Nucleotide - Complementary - DNA - RNA - Hydrogen bond - Adenine - Thymine - Guanine - Cytosine - Uracil

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The following abbreviations are commonly used to describe the length of a DNA/RNA molecule:

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• kbp = kilo base pairs = 1,000 bp
• Mbp = mega base pairs = 1,000,000 bp
• Gbp = giga base pairs = 1,000,000,000 bp

In case of single stranded DNA/RNA we talk about nucleotides, abbreviated nt (or knt, Mnt, Gnt), rather than base pairs, as they are not paired.

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The following figure shows the chemical structures of properly base-paired nucleic acids.

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Chemical structure of base pair bonding

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