A first exploration of a Robertsonian translocation heterozygote in the mouse for its usefulness in cytological evaluation of radiation-induced meiotic autosomal non-disjunction.

In this report some data concerning the male meiotic system of mice heterozygous for Rb(11.13)4Bnr are presented and compared with those of a chromosomally normal Swiss random-bred stock. Change of the genetic background from a C3H/Swiss hybrid situation to the fourth backcross generation (to the Swiss random-bred stock), did not alter the average frequency of aneuploid secondary spermatocytes. This was confirmed by studies on post-implantation loss. Spermatogenic characteristics of Rb4/+ mice, such as testis weight, sperm production and the number of diplotene-metaphase-I figures found in stage XII of the seminiferous epithelium, suggest delay and cell death during this period. These data support our working hypothesis that such an aberrant chromosome system may be more prone to radiation effects and therefore is promising in our cytological studies into the causes of spontaneous and in our cytological studies into the causes of spontaneous and induced autosomal non-disjunction during meiosis in the mouse.