![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Metaphase_spread_of_the_Siberian_Roe_deer_%2528Capreolus_pygargus%2529.jpg/640px-Metaphase_spread_of_the_Siberian_Roe_deer_%2528Capreolus_pygargus%2529.jpg&w=640&q=50)
B chromosome
Type of chromosome / From Wikipedia, the free encyclopedia
This article is about B-chromosomes. For B-DNA, see B-DNA.
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.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Metaphase_spread_of_the_Siberian_Roe_deer_%28Capreolus_pygargus%29.jpg/320px-Metaphase_spread_of_the_Siberian_Roe_deer_%28Capreolus_pygargus%29.jpg)