Recombination between sequences in nonhomologous positions.

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• Dispersed repeated sequences in eukaryotic genomes pose a risk of chromosomal rearrangements through crossing-over.
• The yeast genome's stability implies mechanisms that constrain recombination between these sequences.

Purpose of the Study:

• To investigate the constraints on recombination between dispersed repeated sequences in the yeast genome.
• To determine the frequency and nature of recombination events, including crossovers and gene conversion.
• To explore the role of higher-order chromosome structure in regulating interchromosomal recombination.

Main Methods:

• Construction of yeast strains with two alleles of the his3 gene on different chromosomes.
• Analysis of recombination events, distinguishing between gene conversion and reciprocal translocations.
• Comparison of recombination frequencies between chromosomal and plasmid-borne alleles.

Main Results:

• Gene conversion is the predominant recombination event (majority) between the his3 alleles.
• Approximately 10% of recombination events result in reciprocal translocations.
• Recombination frequency increases 5- to 10-fold when one allele is on an autonomously replicating plasmid compared to chromosomal locations.

Conclusions:

• Higher-order chromosome structure likely plays a role in restricting interchromosomal recombination in yeast.
• The study provides insights into the mechanisms maintaining yeast genome stability despite the presence of dispersed repeats.
• The generated translocation was used to determine gene orientation relative to centromeres.