Control of yeast cell types by mobile genes: A test

Abstract

The yeast Saccharomyces cerevisiae changes cell types of switching the alleles of the mating type locus (MAT) from a to .alpha. and vice versa. In the cassette model, these switches.sbd.e.g., from a to .alpha..sbd.occur when a replica of silent .alpha. information (an .alpha. "cassette") replaces the resident a cassette at the mating type locus and is thereby expressed. A mutation was identified in the locus postulated to be the silent .alpha. information (HML.alpha.). A mutation is introduced into the mating type locus as a result of interconversion: HML.alpha.- MAT.alpha. cells switch to MATa and then to MAT.alpha.-. The MAT.alpha.- mutation leads to defective mating and behaves like some previously identified MAT.alpha.- mutations. These observations satisfy the prediction of the cassette and controlling element models that genetic information is transmitted from HML.alpha. to the mating type locus.