Diploid yeast cells yield homozygous spontaneous mutations

A leucine-requiring hybrid of Saccharomyces cerevisiae, homoallelic at the LEU1/(leu1-12/leu1-12) and heterozygous for three chromosome-7 genetic markers distal to the LEU1 locus, was employed to inquire: (1) whether spontaneous gene mutation and mitotic segregation of heterozygous markers occur in...

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Bibliographic Details
Published in:Current genetics 1993-05, Vol.23 (5-6), p.430-434
Main Authors: Esposito, M.S. (California Univ., Berkeley (USA). Life Sciences Div.. Lawrence Berkeley Lab.), Bruschi, C.V
Format: Article
Language:English
Subjects:
DIPLOIDIA
DIPLOIDIE
Diploidy
Genes, Fungal
Genotype
HETEROCIGOTOS
HETEROZYGOTE
HOMOCIGOTOS
HOMOZYGOTE
Life Sciences (General)
Loss of heterozygosity
MUTACION
MUTATION
Mutational homozygosis
RECOMBINACION
RECOMBINAISON
Recombination
SACCHAROMYCES CEREVISIAE
Saccharomyces cerevisiae - genetics
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Summary:A leucine-requiring hybrid of Saccharomyces cerevisiae, homoallelic at the LEU1/(leu1-12/leu1-12) and heterozygous for three chromosome-7 genetic markers distal to the LEU1 locus, was employed to inquire: (1) whether spontaneous gene mutation and mitotic segregation of heterozygous markers occur in positive nonrandom association and (2) whether homozygous LEU1/LEU1 mutant diploids are generated. The results demonstrate that gene mutation of leu1- 12 to LEU1 and mitotic segregation of heterozygous chromosome-7 markers occur in strong positive nonrandom association, suggesting that the stimulatory DNA lesion is both mutagenic and recombinogenic. In addition, genetic analysis of diploid Leu(+) revertants revealed that approximately 3% of mutations of leu1-12 to LEU1 result in LEU1/LEU1 homozygotes. Red-white sectored Leu(+) colonies exhibit genotypes that implicate postreplicational chromatid breakage and exchange near the site of leu1-12 reversion, chromosome loss, and subsequent restitution of diploidy, in the sequence of events leading to mutational homozygosis. By analogy, diploid cell populations can yield variants homozygous for novel recessive gene mutations at biologically significant rates. Mutational homozygosis may be relevant to both carcinogenesia and the evaluation of asexual diploid organisms
ISSN:0172-8083
1432-0983
DOI:10.1007/BF00312630