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Diploid yeast cells yield homozygous spontaneous mutations
1Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Current Genetics
|May 1, 1993
Summary
Gene mutation and marker segregation in yeast are linked, indicating DNA damage is mutagenic and recombinogenic. This process can lead to homozygous mutants, relevant to cancer and evolution.
Area of Science:
- Molecular biology
- Genetics
- Yeast genetics
Background:
- Investigating spontaneous genetic events in Saccharomyces cerevisiae.
- Understanding the relationship between gene mutation and chromosomal marker segregation.
Purpose of the Study:
- To determine if gene mutation and mitotic segregation of heterozygous markers occur in nonrandom association.
- To ascertain if homozygous LEU1/LEU1 mutant diploids are generated from leu1-12 mutations.
Main Methods:
- Utilizing a leucine-requiring Saccharomyces cerevisiae hybrid, homoallelic at LEU1 (leu1-12/leu1-12).
- Employing heterozygous genetic markers on chromosome VII distal to the LEU1 locus.
- Analyzing diploid Leu+ revertants and red-white sectored colonies.
Main Results:
- Gene mutation (leu1-12 to LEU1) and marker segregation show strong positive nonrandom association.
- Approximately 3% of LEU1 revertants result in LEU1/LEU1 homozygotes.
- Evidence suggests post-replicational chromatid breakage, exchange, chromosome loss, and diploidy restitution.
Conclusions:
- The DNA lesion responsible for leu1-12 reversion is both mutagenic and recombinogenic.
- Mutational homozygosis occurs at significant rates in diploid cell populations.
- Mutational homozygosis has implications for carcinogenesis and asexual diploid organism evolution.