title: Genetic control of sex-chromosomal univalency in the spermatocytes of C57BL/6J and DBA/2J mice.
abstract: The genetic control of sex-chromosomal univalency was examined in the primary spermatocytes of the mouse. The C57BL/6J strain expresses 3% X-Y univalency and DBA/2J expresses 37% univalency. The reciprocal F1 and the eight types of reciprocal backcross males were examined. In the C57BL/6J--DBA/2J strain pair, X--Y univalency is controlled by three genetic systems. Autosomal factors of unknown number that are dominant in DBA/2J increase the probability of univalency from 3% in C57BL/6J to 12%. The DBA/2J-Y chromosome, in place of the C57BL/6J-Y chromosome, has an additive effect to increase the probability of univalency from 12 to 37% in the DBA/2J strain. Two X-chromosome factors that differ between C57BL/6J and DBA/2J regulate the probability of univalency. The X-chromosome factors appear to be separated by sufficient distance so that, with the DBA/2J-Y chromosome and dominant DBA/2J autosomal factors, there are two recombinant classes of X--Y univalency at 20 and 60%. The genetic factors in the univalency trait may be involved in the regulation or structure of the terminal attachment sites between the X and Y chromosomes.
mesh_terms: D000818:Animals; D003433:Crosses, Genetic; D005260:Female; D005799:Genes, Dominant; D007621:Karyotyping; D008297:Male; D008677:Metaphase; D051379:Mice; D008810:Mice, Inbred C57BL / Q000235:genetics*; D008811:Mice, Inbred DBA / Q000235:genetics*; D011336:Probability; D013045:Species Specificity; D013090:Spermatocytes / Q000166:cytology / Q000648:ultrastructure*; D014960:X Chromosome / Q000648:ultrastructure*; D014998:Y Chromosome / Q000648:ultrastructure*