Linkage of genetic markers emt and chr in Chinese hamster cells

Segregation analysis in somatic cell hybrids has been used to demonstrate linkage in the CHO cell line between two autosomal loci, emt (defined by mutants resistant to the protein synthesis inhibitor emetine) and chr (defined by mutants resistant to chromate). In both cases drug resistance behaves recessively in hybrids and linkage has been determined by examining the recovery of the mutant phenotypes from hybrids of the type CHO emtr chrr x CHO emt+ chr+. Of 24 independent segregants selected for resistance to emetine, all 24 were also resistant to chromate while only 18 out of 24 segregants selected for chromate resistance were also resistant to emetine. The biological significane of this "polarity effect" is currently unknown but may be related to the molecular mechanism or mechanisms by which segregation occurs in hybrid cells. In this and the accompanying paper (Worton, Duff, and Campbell) we discuss a number of possible mechanisms of segregation, of which we believe mitotic recombination to be most consistent with the available data.