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Biomedical subjects

S Fogel

Publications and source records attributed to S Fogel.

78 records · Page 5Linked to original sources
PubMed1968

Extraction and isolation of individual ribosomal proteins from Escherichia coli.

We have described a new method for the quantitative separation of ribosomal proteins and ribosomal ribonucleic acid. A procedure for the preparation of individual ribosomal proteins by polyacrylamide gel electrophoresis is also described. By the use of gels with smaller pores, at least four of the electrophoretic components from the 30S ribosome can be split into additional protein fractions. By the methods described here, it is possible to isolate in high purity at least 15 different proteins from the 30S ribosome of Escherichia coli.

Bacterial Proteins↗
PubMedDate not supplied

Mismatch-specific post-meiotic segregation frequency in yeast suggests a heteroduplex recombination intermediate.

Post-meiotic segregation of alleles, which is seen, for example, in the 5:3 distribution of alleles in the products of a single meiosis in fungi, has been thought to be due to the non-repair of heteroduplex regions formed during genetic recombination. In current models of genetic recombination, heteroduplex DNA is formed either as the primary intermediate generated by two interacting non-sister chromatids or as a short region flanking a double-stranded gap. The frequency of post-meiotic segregation differs for different alleles, and this is presumed to reflect the varying efficiencies with which different types of mismatches in the heteroduplex are repaired. To gain some insight into this process, we have now determined the nucleotide sequences of various yeast alleles with different post-meiotic segregation frequencies and compared the mismatches predicted to occur in heteroduplexes of these alleles with wild-type DNA with those repaired with varying efficiency in bacterial systems. A striking correlation is observed, with the mismatches predicted for high post-meiotic segregation frequency alleles being similar to mismatches repaired with low efficiency in bacteria. These results support the view that postmeiotic segregation frequency reflects heteroduplex repair efficiency and the contention that meiotic gene conversion is the result of the successful repair of heteroduplex mismatches.

DNA Repair↗
PubMedDate not supplied

The role of heteroduplex correction in gene conversion in Saccharomyces cerevisiae.

Two different models have been proposed to explain the relative frequencies of the non-mendelian allelic segregations which are detected by tetrad analysis after meiosis in fungi. The first model maintains that 6:2 type tetrads result from correction of heteroduplexes containing mismatched sites and 5:3 type tetrads result from failure to correct mismatched sites. The second model suggests that 6:2 segregations result from the filling-in of double-strand gaps using information obtained from both strands of a homologous duplex. In this model 5:3 type tetrads result if the allele is included in the heteroduplex regions flanking the gap and the resulting mismatched nucleotides are not corrected. We have studied the correction of heteroduplex plasmid DNA in pms1 mutant strains of Saccharomyces cerevisiae, which are known to exhibit higher frequencies of 5:3 type tetrads and lower frequencies of 6:2 tetrads than wild-type strains. Our results suggest that the pms1 mutation causes a defect in mismatch correction, supporting the hypothesis that meiotic gene conversion in wild-type yeast cells often results from the correction of heteroduplex DNA.

DNA Repair↗