The T6 translocation in the mouse: its use in trisomy mapping, centromere localization, and cytological identification of linkage group 3.

The occurrence of hairless piebald mice trisomic for the chromosome segments of the T6M chromosome has shown that the LG III loci hr and s are not located on T6M. The T6 breakpoint in LG III is therefore in the position hr-s-T6. T6M must carry the gene Fkl, which is located on the far side of the T6 breakpoint from hr in LG III.-T6 reduces recombination in the hr-s region.-Trisomy for the chromosome segments of the T6M chromosome appears to severely reduce viability.-The gene hr has been shown to lie between the centromere and the T6 breakpoint. The order of loci in LG III is therefore: centromere-hr-s-T6.-Equations are given for the relation between the frequency of adjacent-2 segregation and the frequency of recovery of complementation zygotes for the case in which the translocation heterozygote can form either quadrivalent or univalent-trivalent configurations at meiosis.-Linkage Group III is carried on chromosome 14. LG VI is the other linkage group involved in T6, and is carried on chromosome 15.