INDEPENDENT CHROMOSOME SEGREGATION AND ABSENCE OF INTERCHROMOSOMAL EFFECT AT FIRST MEIOTIC DIVISION IN MALE CHINESE-HAMSTERS HETEROZYGOUS FOR 2 RECIPROCAL TRANSLOCATIONS

Chromosome segregation and interchromosomal effects of reciprocal tran slocations at first meiotic division were investigated by chromosome a nalysis of meiotic cells from male Chinese hamsters heterozygous for t wo reciprocal translocations. We used six stocks heterozygous for two different translocations which were obtained by crosses between males and females homozygous or heterozygous for a different translocation. The frequency of second meiotic (MII) cells from each segregational cl ass of one quadrivalent in heterozygotes for two reciprocal translocat ions agreed with that of the same quadrivalent in heterozygotes for th e single translocation. This indicates that the two quadrivalents in h eterozygotes for two reciprocal translocations segregate independently . The mean frequency of hyperhaploid MII cells from males heterozygous for two reciprocal translocations ranged from 7.1 to 15.4%. These cel ls were mostly derivatives from 3:1 disjunctions of the quadrivalents. The percentage of cells with extra chromosomes in translocation-unrel ated groups was calculated at 0.10-0.25 %. The frequency did not incre ase significantly as compared with that in karyotypically normal males , in which the mean frequency of hyperhaploid MII cells was 0.39%. The se findings revealed that reciprocal translocations do not have interc hromosomal effects on meiotic division in male Chinese hamsters.