Statistical tests for detecting gene conversion

Statistical tests for detecting gene conversion are described for a sampleof homologous DNA sequences. The tests are based on imbalances in thedistribution of segments on which some pair of sequences agrees. Themethods automatically control for variable mutation rates along the genomeand do not depend on a priori choices of potentially monophyletic subsetsof the sample. The tests show strong evidence for multiple intragenicconversion events at two loci in Escherichia coli. The gnd locus in E. colishows a highly significant excess of maximal segments of length 70-200 bp,which suggests conversion events of that size. The data also indicate thatthe rate of these short conversion events might be of the order of neutralmutation rate. There is also evidence for correlated mutation in adjacentcodon positions. The same tests applied to a locus in an RNA virus werenegative.