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  • 1
    Electronic Resource
    Electronic Resource
    Nonrandomly-associated forward mutation and mitotic recombination yield yeast diploids homozygous for recessive mutations (1994)
    Springer
    Current genetics 26 (1994), S. 302-307 
    Details
    ISSN: 1432-0983
    Keywords: S. cerevisiae ; Spontaneous mutation ; Mitotic segregation ; Loss of heterozygosity ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have employed the analysis of spontaneous forward mutations that confer the ability to utilize L-α-aminoadipate as a nitrogen source (α-Aa+) to discern the events that contribute to mitotic segregation of spontaneous recessive mutations by diploid cells. α-Aa- diploid cells yield α-Aa+ mutants at a rate of 7.8±3.6×10-9. As in haploid strains, approximately 97% (30/31) of α-Aa+ mutants are spontaneous lys2-x recessive mutations. α-Aa+ mutants of diploid cells reflect mostly the fate of LYS2/lys2-x heterozygotes that arise by mutation within LYS2/LYS2 populations at a rate of 1.2±0.4×10-6. Mitotic recombination occurs in nonrandom association with forward mutation of LYS2 at a rate of 1.3±0.6×10-3. This mitotic recombination rate is tenfold higher than that of a control LYS2/lys2-1 diploid. Mitotic segregation within LYS2/lys2-x subpopulations yields primarily lys2-x/lys2-x diploids and a minority of lys2-x aneuploids. Fifteen percent of lys2-x/lys2-x diploids appear to have arisen by gene conversion of LYS2 to lys2-x; 85% of lys2-x/lys2-x diploids appear to have arisen by mitotic recombination in the CENII-LYS2 interval. lys2-1/lys2-1 mitotic segregants of a control LYS2/lys2-1 diploid consist similarly of 18% of lys2-1/lys2-1 diploids that appear to have arisen by gene conversion of LYS2 to lys2-1 and 82% of lys2-1/lys2-1 diploids that appear to have arisen by mitotic recombination in the CENII-LYS2 interval. The methods described can be used to simultaneously monitor the effects of yeast gene mutations and carcinogens on the principal parameters affecting the genomic stability of diploid mitotic cells: mutation, gene conversion, intergenic recombination, and chromosomal loss or rearrangement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310493
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  • 2
    Electronic Resource
    Electronic Resource
    Simultaneous detection of changes in chromosome number, gene conversion and intergenic recombination during mitosis of Saccharomyces cerevisiae: spontaneous and ultraviolet light induced events (1982)
    Springer
    Current genetics 6 (1982), S. 5-11 
    Details
    ISSN: 1432-0983
    Keywords: Chromosomal loss ; Mitotic nondisjunction ; Gene conversion ; Mitotic recombination ; Ultraviolet light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have employed a hyperhaploid strain of Saccharomyces cerevisiae disomic for chromosome VII to monitor spontaneous and ultraviolet light induced restitution of haploidy (chromosomal loss and/or nondisjunction), mitotic gene conversion and mitotic intergenic recombination. The disomic chromosomal pair incorporates six heterozygous markers, including cyh2 r, distributed on both sides of the centromere. Cycloheximide resistant segregants of spontaneous origin were analyzed to calculate the spontaneous mitotic rates of restitution of haploidy, intergenic recombination and gene conversion that result in expression of the cyh2 r mutation. Restitution of haploidy was found to be the most common source of spontaneously arising cycloheximide resistant segregants. In contrast, those induced by ultraviolet light resulted most frequently from gene conversion of CYH2 s to cyh2 r. The chromosome VII hyperhaploid system provides a sensitive method to detect the aneugenic and recombinagenic effects of suspect chemical and physical agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397633
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