The G and Q banding pattern of Ellobius lutescens. A unique case of sex determination in mammals.

The karyotype of the microtine Ellobius lutescens Th., was analysed using the G and Q banding techniques. One of the chromsomes of the first pair has the same bands in both sexes while the other member of the pair is unique to each sex. We propose that the sex determining mechanism of Ellobius lutescens is located in these chromosomes. The genetic burden imposed on this species due to this constitution is discussed.