Gene conversion, unequal crossing-over and mispairing at a non-tandem duplication during meiosis ofSaccharomyces cerevisiae
✍ Scribed by Daniel H. Maloney; Seymour Fogel
- Publisher
- Springer-Verlag
- Year
- 1987
- Tongue
- English
- Weight
- 651 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0172-8083
No coin nor oath required. For personal study only.
✦ Synopsis
We have developed a novel system to examine conversion, exchange and mispairing involving a nontandem duplication of the ade8 locus in yeast by monitoring the segregation of heterozygous markers between the duplicated sequence. P1asmid Yrp17 carries the yeast selectable markers URA3 + and TRP1 +. Yrp 17 derivatives with a 4 kb insert carrying ade8-18 were used to clone the mutations trpl-1 and ura3-1 by gap repair. Integrants of the resulting plasmids at the Ade8 locus were crossed to yield diploid hybrids with a non-tandem duplication of Ade8 and heterozygosity for the plasmid markers between the duplicated sequences. 1192 complete, unselected asci were analyzed and 270 exhibiting recombination of the markers contributed by the plasmid were analyzed by Southern transfers to detect changes in plasmid sequences. Twenty-seven tetrads had unequal homologous exchanges and five had unequal sister-chromatid exchanges. Seven tetrads carry an additional copy of the integrated plasmid and ten are missing one. We propose that these two classes represent conversions of the entire 11 kb plasmid, which occur after misalignment and formation of an unpaired loop. Mispairing is a frequent event, and occurs in approximately fifty percent of all meioses. The system described provides a means to determine the meiotic rules of conversion, exchange and pairing for duplicated DNA sequences.