The b chromosome system of omocestus bolivari: Changes in b-behaviour in m4-polysomic b-males

Abstract

A metacentric B chromosome has been found in four out the five populations of Omocestus bolivari analysed. The B univalent frequently associates with the X chromosome at prophase I. The iso-B nature is deduced from the persistent association between the two arms of the B, but it is neither confirmed nor denied by its C-banding response. At first meiotic division B univalents sometimes divide equationally which lead to their loss in the form of microspermatids. These aspects of meiotic behaviour of the iso-B's are significantly influenced by the M4-polysomy. © 1985 The Genetical Society of Great Britain.