RANDOMNESS IN THE FORMATION OF RADIATION-INDUCED CHROMOSOME ABERRATIONS

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Abstract
The frequencies of asymmetrical and symmetrical exchanges induced in G1 chromosomes of Vicia have been found to be equal. This is expected if the 2 types of exchange arise with equal probability from a single chromosomal configuration (site) by random adjoining of broken ends. It is suggested that previous reports of inequality of the frequencies of the 2 exchange types are a result of scoring artifacts not present in this experiment. The relative frequency with which the M [Meta-centric] and S [Subtelocentric] chromosomes enter into exchanges is similar for chromosomes and chromatids, the M chromosome being involved less frequently (and consequently the S chromosomes more frequently) than expected on the basis of metaphase length.