Induction by X-rays of chromosomal aberrations in somatic and germ cells of mice with different karyotypes.

Stem-cell spermatogonia of +/+, T70H translocation heterozygous and Ts(1(13))70H tertiary trisomic mice were irradiated with various doses of x-rays. Blood lymphocytes of +/+ and Ts(1(13))70H males were irradiated with 150 rad X-rays. Contrary to earlier findings (De Boer et al., 1977), tertiary trisomic mice with morphological abnormalities did not show an increased sensitivity for radiation-induced chromosome breaks. The yields of radiation-induced reciprocal translocations, scored in the primary spermatocytes, were equal for the +/+ and tertiary trisomic mice but were lower for the T70/+ males. Thus, no parallel could be established with the sensitivity of peripheral blood lymphocytes for the induction of dicentric chromosomes, where T70H/+ did not differ from +/+ mice (De Boer et al., 1977). Induced reciprocal translocations occurred randomly over late diplotene-early diakinesis and late diakinesis-metaphase I stages. Among the T70H/+ males (2 x 500 rad) there was no relation between the chiasma frequency per animal and the yield of induced translocations, though the translocation induction was positively correlated with the chiasma frequency on a per-cell basis. When all descendants of irradiated T70H spermatogonia were pooled, the induced translocation-originated multivalent contained more chiasmata in cells that had a higher chiasma score themselves. No relation could be found between the yield of induced translocations and the recovery of spermatogenesis after irradiation as expressed by the epididymal sperm count after 2 x 500 rad.