bp

Definition

Abbreviation for base pair, the fundamental unit of double-stranded DNA or RNA length consisting of two complementary nucleotides (adenine-thymine or guanine-cytosine in DNA; adenine-uracil or guanine-cytosine in RNA) joined by hydrogen bonds. In arthropod genomics, genome size is commonly expressed in megabases (Mb; millions of bp), with insects showing extraordinary variation—from the tiny 58 Mb genome of the Antarctic midge Belgica antarctica to the 16,500 Mb genome of the mountain grasshopper Podisma pedestris. The term also denotes the physical distance between nucleotide positions on a chromosome, making it essential for describing gene locations, quantitative trait loci, and comparative synteny studies across species.

Etymology

Initialism of 'base pair', first used in molecular biology literature in the 1960s as DNA sequencing and genome sizing became routine

Example

The jewel wasp Nasonia vitripennis was among the first parasitoid insects to have its genome sequenced, revealing a compact genome of approximately 297 Mb (297 million bp) with notably low repetitive DNA content compared to other hymenopterans.

Synonyms

• Base pair

Related Terms

• genome size
• megabase
• Nucleotide
• karyotype
• synteny
• scaffold
• contig
• whole genome sequencing
• comparative genomics

Usage Notes

Always used as a countable unit for length measurement, never for single-stranded sequence (where 'nt' for nucleotide is preferred). In formal scientific writing, 'bp' is lowercase and unitalicized; 'Mb' (megabase) and 'Gb' (gigabase) follow for larger scales. Distinct from 'bp' as basis point in finance or 'BP' as British Petroleum. When referring to genome assemblies, 'bp' typically describes total span including gaps, while 'total non-gap bp' or 'assembled bp' specifies contiguous sequence. The plural form is identical: 'the genome contains 180 million bp'.