Autoradiographic Visualisation of Paternal Chromosomes in Mouse Eggs

Abstract

THE paternal component of the genome has been localised in the nuclear chromatin of early cleaving mouse eggs¹ by autoradiography following the mating of normal females with males in which the spermatogonial cell line was labelled in vivo with tritiated thymidine (³H-TdR). The results indicated that in at least the earliest developmental stages of the mouse zygote there is a separation of maternal and paternal chromatin. This extends to mammals the concept of gonomery well known in lower animals². The interpretation of these findings, as well as further exploitation of this experimental system, relies on the distribution of paternal labelled chromosomes at metaphase in early cleavage. An expected separation into twenty labelled and twenty unlabelled chromosomes is most unlikely to occur by chance. Here we present an analysis of the distribution pattern of the labelling in chromosomes.