B chromosome

This article is about B-chromosomes. For B-DNA, see B-DNA.
Siberian roe deer metaphase spread with B chromosomes

In addition to the normal karyotype, wild populations of many animal, plant, and fungi species contain B chromosomes (also known as supernumerary, accessory, (conditionally-)dispensable, or lineage-specific chromosomes).[1] By definition, these chromosomes are not essential for the life of a species, and are lacking in some (usually most) of the individuals. Thus a population would consist of individuals with 0, 1, 2, 3 (etc.) B chromosomes.[1] B chromosomes are distinct from marker chromosomes or additional copies of normal chromosomes as they occur in trisomies.

  1. ^ a b White, M. J. D. (1973). The chromosomes (6th ed.). London: Chapman and Hall. p. 171. ISBN 0-412-11930-7.