Editing Base pair (section)

==Length measurements==<!-- This section is linked from [[KB]] -->
{{redirect|Gbp|other uses|GBP (disambiguation)}}
[[File:Human karyotype with bands and sub-bands.png|thumb|Schematic [[karyotype|karyogram]] of a human. The blue scale to the left of each nuclear chromosome pair (as well as the [[human mitochondrial genetics|mitochondrial genome]] at bottom left) shows its length in terms of mega–base-pairs.<br>{{further|Karyotype}}]]
The following abbreviations are commonly used to describe the length of a D/R[[DNA|NA molecule]]:
* bp  = base pair—one bp corresponds to approximately 3.4&nbsp;[[Angstrom|Å]] (340&nbsp;[[picometre|pm]])<ref>{{cite book| vauthors = Alberts B, Johnson A, Lewis J, Morgan D, Raff M, Roberts K, Walter P |title=Molecular Biology of the Cell|date=December 2014|publisher=Garland Science, Taylor & Francis Group|location=New York/Abingdon|isbn=978-0-8153-4432-2|page=177|edition=6th|ref=alberts_mboc}}</ref>  of length along the strand, and to roughly 618 or 643 [[Atomic mass units|daltons]] for DNA and RNA respectively.
* kb (= kbp) = kilo–base-pair = 1,000 bp
* Mb (= Mbp) = mega–base-pair = 1,000,000 bp
* Gb (= Gbp) = giga–base-pair = 1,000,000,000 bp

For single-stranded DNA/RNA, units of [[nucleotide]]s are used—abbreviated nt (or knt, Mnt, Gnt)—as they are not paired.
To distinguish between units of [[computer storage]] and bases, kbp, Mbp, Gbp, etc. may be used for base pairs.

The [[centimorgan]] is also often used to imply distance along a chromosome, but the number of base pairs it corresponds to varies widely. In the human genome, the centimorgan is about 1 million base pairs.<ref>{{cite web |url=http://rarediseases.info.nih.gov/Glossary.aspx?acronym=False#C |title=NIH ORDR – Glossary – C |publisher=Rarediseases.info.nih.gov |access-date=2012-07-16 |archive-date=2012-07-17 |archive-url=https://web.archive.org/web/20120717121400/http://rarediseases.info.nih.gov/Glossary.aspx?acronym=False#C |url-status=dead }}</ref><ref>{{cite book |vauthors=Scott MP, Matsudaira P, Lodish H, Darnell J, Zipursky L, Kaiser CA, Berk A, Krieger M |title=Molecular Cell Biology |edition=Fifth |publisher=W. H. Freeman |location=San Francisco |date=2004 |page=[https://archive.org/details/molecularcellbio00harv/page/396 396] |isbn=978-0-7167-4366-8 |quote=...in humans 1 centimorgan on average represents a distance of about 7.5x10<sup>5</sup> base pairs. |url-access=registration |url=https://archive.org/details/molecularcellbio00harv/page/396 }}</ref>