Resolution of recombination intermediates generated during yeast mating type switching

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• Interchromosomal gene conversion in yeast often correlates with the recombination of nearby genetic markers.
• Gene conversion between alleles at the mating-type (MAT) locus in yeast, triggered by the homothallic switching system, also typically involves recombination.

Purpose of the Study:

• To investigate whether crossing-over accompanies gene conversion between non-allelic HMR and MAT genes when initiated by the homothallic switching system in yeast.
• To compare the recombination patterns of gene conversion at the MAT locus versus between HMR and MAT loci.

Main Methods:

• Utilizing the homothallic switching system in yeast to initiate gene conversion events.
• Analyzing genetic markers flanking the HMR and MAT loci to detect recombination.
• Comparing gene conversion events at the MAT locus with those between HMR and MAT loci.

Main Results:

• Gene conversion between alleles at the MAT locus initiated by the homothallic switching system is associated with recombination of flanking markers.
• No evidence of crossing-over was found accompanying gene conversion between the non-allelic HMR and MAT genes, even when initiated by the same homothallic switching system.

Conclusions:

• The homothallic switching system in yeast can mediate gene conversion between non-allelic loci (HMR and MAT) without associated crossing-over.
• This finding suggests a distinction in the recombination mechanisms or pathways involved in gene conversion depending on whether alleles are at the same locus (allelic) or different loci (non-allelic).