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The role of Exo1p exonuclease in DNA end resection to generate gene conversion tracts in Saccharomyces cerevisiae.

Yin Y, Petes TD - Genetics (2014)

Bottom Line: In accordance with this expectation, gene conversion tract lengths associated with spontaneous crossovers in exo1 strains were reduced about twofold relative to wild type.For UV-induced events, conversion tract lengths associated with crossovers were also shorter for the exo1 strain than for the wild-type strain (3.2 and 7.6 kb, respectively).Unexpectedly, however, the lengths of conversion tracts that were unassociated with crossovers were longer in the exo1 strain than in the wild-type strain (6.2 and 4.8 kb, respectively).

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina 27710.

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Related in: MedlinePlus

Colony-sectoring assay for detecting mitotic crossovers. The diploids in our study are homozygous for the ade2-1 ochre mutation. Diploids with this mutation form red, pink, or white colonies, depending on whether they contain zero, one, or two copies of the SUP4-o ochre suppressor tRNA gene, respectively. In our experiments, the diploids were heterozygous for the SUP4-o that was located near the end of either the left arm of chromosome V or the right arm of chromosome IV. These diploids form pink colonies. However, a crossover between SUP4-o and the centromere results in a red/white sectored colony. Note that only half of the crossovers are detected by the sectoring assay. If chromatids 1 and 4, and 2 and 3, cosegregate, a sectored colony is not formed.
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fig2: Colony-sectoring assay for detecting mitotic crossovers. The diploids in our study are homozygous for the ade2-1 ochre mutation. Diploids with this mutation form red, pink, or white colonies, depending on whether they contain zero, one, or two copies of the SUP4-o ochre suppressor tRNA gene, respectively. In our experiments, the diploids were heterozygous for the SUP4-o that was located near the end of either the left arm of chromosome V or the right arm of chromosome IV. These diploids form pink colonies. However, a crossover between SUP4-o and the centromere results in a red/white sectored colony. Note that only half of the crossovers are detected by the sectoring assay. If chromatids 1 and 4, and 2 and 3, cosegregate, a sectored colony is not formed.

Mentions: To distinguish among the patterns of LOH shown in Figure 1 and to map the positions of the LOH, we used diploids generated by crossing two sequence-diverged haploids, W303a and YJM789 (St. Charles and Petes 2013; Yin and Petes 2013). This diploid, in addition to being heterozygous for SNPs located throughout the genome, contained markers on either chromosome V (YYy29.8) or chromosome IV (YYy34) that allowed identification of reciprocal crossovers (Figure 2). The diploids are homozygous for ade2-1, an ochre mutation. In the presence of zero, one, and two copies of the ochre suppressor SUP4-o, the diploids form red, pink, and white colonies, respectively (Barbera and Petes 2006). The SUP4-o gene is integrated near the telomeres of chromosomes V (YYy29.8) and IV (YYy34) in the strains used in our study. In these diploids, crossovers between the centromere and the heterozygous SUP-o marker produce red/white sectored colonies. Only half of the crossover events are detectable by this system (Chua and Jinks-Robertson 1991), since cosegregation of two recombined chromosomes into one daughter cell and two unrecombined chromosomes into the other daughter does not lead to LOH.


The role of Exo1p exonuclease in DNA end resection to generate gene conversion tracts in Saccharomyces cerevisiae.

Yin Y, Petes TD - Genetics (2014)

Colony-sectoring assay for detecting mitotic crossovers. The diploids in our study are homozygous for the ade2-1 ochre mutation. Diploids with this mutation form red, pink, or white colonies, depending on whether they contain zero, one, or two copies of the SUP4-o ochre suppressor tRNA gene, respectively. In our experiments, the diploids were heterozygous for the SUP4-o that was located near the end of either the left arm of chromosome V or the right arm of chromosome IV. These diploids form pink colonies. However, a crossover between SUP4-o and the centromere results in a red/white sectored colony. Note that only half of the crossovers are detected by the sectoring assay. If chromatids 1 and 4, and 2 and 3, cosegregate, a sectored colony is not formed.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4125386&req=5

fig2: Colony-sectoring assay for detecting mitotic crossovers. The diploids in our study are homozygous for the ade2-1 ochre mutation. Diploids with this mutation form red, pink, or white colonies, depending on whether they contain zero, one, or two copies of the SUP4-o ochre suppressor tRNA gene, respectively. In our experiments, the diploids were heterozygous for the SUP4-o that was located near the end of either the left arm of chromosome V or the right arm of chromosome IV. These diploids form pink colonies. However, a crossover between SUP4-o and the centromere results in a red/white sectored colony. Note that only half of the crossovers are detected by the sectoring assay. If chromatids 1 and 4, and 2 and 3, cosegregate, a sectored colony is not formed.
Mentions: To distinguish among the patterns of LOH shown in Figure 1 and to map the positions of the LOH, we used diploids generated by crossing two sequence-diverged haploids, W303a and YJM789 (St. Charles and Petes 2013; Yin and Petes 2013). This diploid, in addition to being heterozygous for SNPs located throughout the genome, contained markers on either chromosome V (YYy29.8) or chromosome IV (YYy34) that allowed identification of reciprocal crossovers (Figure 2). The diploids are homozygous for ade2-1, an ochre mutation. In the presence of zero, one, and two copies of the ochre suppressor SUP4-o, the diploids form red, pink, and white colonies, respectively (Barbera and Petes 2006). The SUP4-o gene is integrated near the telomeres of chromosomes V (YYy29.8) and IV (YYy34) in the strains used in our study. In these diploids, crossovers between the centromere and the heterozygous SUP-o marker produce red/white sectored colonies. Only half of the crossover events are detectable by this system (Chua and Jinks-Robertson 1991), since cosegregation of two recombined chromosomes into one daughter cell and two unrecombined chromosomes into the other daughter does not lead to LOH.

Bottom Line: In accordance with this expectation, gene conversion tract lengths associated with spontaneous crossovers in exo1 strains were reduced about twofold relative to wild type.For UV-induced events, conversion tract lengths associated with crossovers were also shorter for the exo1 strain than for the wild-type strain (3.2 and 7.6 kb, respectively).Unexpectedly, however, the lengths of conversion tracts that were unassociated with crossovers were longer in the exo1 strain than in the wild-type strain (6.2 and 4.8 kb, respectively).

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina 27710.

Show MeSH
Related in: MedlinePlus