Definition of B chromosome in English:

B chromosome

noun

Genetics
  • 1Disused A chromosome reckoned as the second in various classifications; now disused.

  • 2A small extra chromosome, found especially in plants and invertebrates, which has no equivalent in the basic chromosome set of a species, and has an irregular, non-Mendelian, mode of inheritance.

Origin

Early 20th century; earliest use found in American Naturalist.