Assuntos
Resistência a Medicamentos/genética , Plantas Geneticamente Modificadas/genética , Resistência a Ampicilina/genética , Anti-Infecciosos , Biomarcadores , Cinamatos/metabolismo , DNA de Plantas/genética , Humanos , Higromicina B/análogos & derivados , Higromicina B/metabolismo , Resistência a Canamicina/genética , Neomicina/metabolismo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/efeitos adversos , Recombinases/metabolismo , Espectinomicina , Estreptomicina/metabolismo , Transformação Bacteriana/genética , beta-Lactamases/genéticaRESUMO
We tested predictions of the double-strand break repair (DSBR) model for meiotic recombination by examining the segregation patterns of small palindromic insertions, which frequently escape mismatch repair when in heteroduplex DNA. The palindromes flanked a well characterized DSB site at the ARG4 locus. The "canonical" DSBR model, in which only 5' ends are degraded and resolution of the four-stranded intermediate is by Holliday junction resolvase, predicts that hDNA will frequently occur on both participating chromatids in a single event. Tetrads reflecting this configuration of hDNA were rare. In addition, a class of tetrads not predicted by the canonical DSBR model was identified. This class represented events that produced hDNA in a "trans" configuration, on opposite strands of the same duplex on the two sides of the DSB site. Whereas most classes of convertant tetrads had typical frequencies of associated crossovers, tetrads with trans hDNA were parental for flanking markers. Modified versions of the DSBR model, including one that uses a topoisomerase to resolve the canonical DSBR intermediate, are supported by these data.
Assuntos
Reparo do DNA , DNA Fúngico , Conversão Gênica , Modelos Genéticos , Ácidos Nucleicos Heteroduplexes , Saccharomyces cerevisiae/genética , Troca Genética , Dano ao DNARESUMO
In yeast meiosis, crossing-over between homologues is dependent upon double-strand breaks. We demonstrate that the occurrence of these breaks is independent of pairing between homologues by showing that they occur with normal frequency, timing, and position in the absence of a homologue. This observation supports models that view double-strand breaks as initiating events and crossing-over as a consequence of repair of these breaks.
Assuntos
Meiose , Recombinação Genética , Saccharomyces cerevisiae/genética , Cromossomos Fúngicos , DNA Fúngico/análise , DNA Fúngico/metabolismo , Cinética , Saccharomyces cerevisiae/citologia , Especificidade da Espécie , Esporos Fúngicos/fisiologia , Fatores de TempoRESUMO
The product of the RAD3 gene of Saccharomyces cerevisiae is required for mitotic cell viability and excision repair of UV-induced pyrimidine dimers. Certain rad3 mutant alleles (originally called rem1) increase the rates of both spontaneous mitotic recombination and mutation. The increase in mutation rates is not dependent upon the presence of the RAD6 error-prone pathway. The mutator phenotype suggests that the wild-type RAD3 gene product may be involved in the maintenance of fidelity of DNA replication in addition to its known role in excision repair. To investigate the role that RAD3 might play in mutation avoidance, we have utilized a well-characterized shuttle vector system to study the mutational spectrum occurring in rad3-102 strains and compare it to that seen in RAD3 strains. The results put constraints on the role that the rad-102 mutant gene product must play if the RAD3 protein is a component of the replication complex. Alternatively, the mutational spectrum is consistent with the hypothesis that the rad3-102 mutant protein interferes with postreplication mismatch repair.
