Genetically controlled chromosome breakage and reunions in the meiosis

Three mutants of Pisum sativum showing anomalies in the conjugation phase of meiosis, were investigated cytogenetically. Inspite of apparent normal chromosome pairing there is a strong reduction of chiasma number resulting into univalent formation. Simultaneously, chromosome aberrations appear as consequence of breakage and reunions in the prophase stage. The combined occurrence of these anomalies and their respective quantitative relationships to each other have been explained in the light of breakage-reunion hypothesis through the action of following factors: pairing behaviour, breakage frequency, number of breakages at one locus in the chromatid tetrads, behaviour of breakage ends and effects of environment. Due to the interaction of these factors all the anomalies found in our mutants are explainable.This study was supported by the Euratom I.T.A.L. and the Ministry of Science and Education, BRD. The second author is presently on a post doctoral fellowship of the Humboldt-Foundation.