Asymmetric Effects of Deletions and Substitutions on High Negative Interference in Coliphage Lambda
AUTOR(ES)
Makin, G. J. Vance
RESUMO
Experiments have been performed to help clarify the role of nonhomologies in phage λ recombination. Three-factor crosses were carried out, and the frequencies of single and double recombinants in the two adjoining intervals were compared when the central marker was either a double point mutation (v1v3) or deletion (rex-cI deletion) or nonhomologous substitution (imm434). In all cases the lefthand marker was a bio substitution (Fec- phenotype, which does not permit plating on recA-), and the righthand marker was an amber mutation in gene O. Experiments were performed in all four possible arrangements of the central and rightward markers, while selecting for the Fec+ phenotype on the recA- host. As anticipated, high negative interference (HNI) was observed with point mutations, but when the central marker was a substitution nonhomology, HNI was reduced about tenfold. Surprisingly, when the central marker was a simple deletion, a dramatic asymmetry in results was observed, with HNI being exhibited only when the central deletion marker was acquired by the double recombinant. These results indicate that under normal conditions (red+, gam+, rec+) and with noninhibited DNA replication, recombination in coliphage λ entails a highly asymmetric step that could be at the level of strand transfer or mismatch repair.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1201942Documentos Relacionados
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