Reciprocal Exchanges Instigated by Large Heterologies in the B2 Gene of Ascobolus Are Not Associated with Long Adjacent Hybrid DNA Stretches
AUTOR(ES)
Langin, T.
RESUMO
In the gene b2 of Ascobolus immersus, large heterologies increase the frequencies of reciprocal exchanges on their upstream border (corresponding to the high non-Mendelian segregation side). Tests were made to determine whether these reciprocal exchanges, instigated by large heterologies, resulted from the blockage of a Holliday junction bordering a hybrid DNA tract extending from the end of the gene to the heterology. Three types of experiments were performed to answer this question. In all cases, results did not correlate the presence of reciprocal exchanges instigated by large heterologies with the presence of adjacent hybrid DNA tracts. These reciprocal exchanges were rarely associated with postmeiotic segregation at upstream markers, they were not associated with gene conversion of a marker within the interval and their frequency was not decreased by decreasing the frequency of hybrid DNA formation in the gene. These results led to the proposal of the existence of a precursor to reciprocal exchange different from a single branch-migrating Holliday junction. This precursor migrates rightward and its migration is dependent on the DNA sequence homology. The existence of this precursor does not exclude that reciprocal exchanges resulting from the maturation of single Holliday junctions bordering adjacent hybrid DNA tracts could also occur.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1203415Documentos Relacionados
- Hybrid DNA tracts may start at different sites during meiotic recombination in gene b2 of Ascobolus
- Disparity of gene conversion in frameshift mutants located in locus b2 of Ascobolus immersus
- Isolation of the Ascobolus Immersus Spore Color Gene B2 and Study in Single Cells of Gene Silencing by Methylation Induced Premeiotically
- Premeiotic and Meiotic Instability Generates Numerous b2 Mutation Derivatives in Ascobolus
- Intragenic Suppression at the b2 Locus in ASCOBOLUS IMMERSUS. I. Identification of Three Distinct Groups of Suppression