POIKILOPLOIDY AMONG SPERMATOGENIC CELLS OF MUS MUSCULUS

Open Access
Publisher Website
Google Scholar
Abstract
Summary. Chromosome counts were made of 431 spermatogonia and 400 primary spermatocytes from forty mice (representing four different genetic stocks, and two different ages) in order to determine the kind and extent of heteroploidy in germ-line cells. In 18% of the spermatogonia, the chromosome number was hypodiploid or hyperdiploid. No heterogeneity in regard to the distribution of these heteroploid cells among the various strain or age groups was found. On the other hand, 7·2% of spermatogonia observed were polyploid and one strain was shown to possess a significantly higher proportion than the other strains. The older males had fewer polyploid spermatogonia, all of which were tetraploid, whereas triploid, tetraploid, hexaploid and octoploid cells were seen in the group of young males. Only 4·7% of the primary spermatocytes were heteroploid and all of these heteroploid cells were close to diploid. It is concluded that heteroploidy (particularly polyploidy) is a real phenomenon in spermatogonia and is in part genetically determined. Polyploid cells probably arise as a result of nuclear fusion among nuclei of the testicular syncytia. The much lower frequency of heteroploidy in primary spermatocytes than among spermatogonia is postulated to be attributable to an important function of the meiotic process.