Asymmetric directional mutation pressures in bacteria.

ABSTRACT: BACKGROUND:When there are no strand-specific biases in mutation and selection rates (that is, in the substitution rates) between the two strands of DNA, the average nucleotide composition is theoretically expected to be A = T and G = C within each strand. Deviations from these equalities are therefore evidence for an asymmetry in selection and/or mutation between the two strands. By focusing on weakly selected regions that could be oriented with respect to replication in 43 out of 51 completely sequenced bacterial chromosomes, we have been able to detect asymmetric directional mutation pressures. RESULTS:Most of the 43 chromosomes were found to be relatively enriched in G over C and T over A, and slightly depleted in G+C, in their weakly selected positions (intergenic regions and third cod

SUBMITTER: Lobry JR 

PROVIDER: S-EPMC134625 | biostudies-literature | 2002 Sep

REPOSITORIES: biostudies-literature