Induced changes in gene conversion spectra

Abstract

IN crosses, segregation at a heterozygous site may produce a low frequency of octads with spore ratios of 6+: 2mutant or 2+: 6m (meiotic segregation), or 5+: 3m or 3+: 5m (postmeiotic segregation), instead of the usual 4+: 4m ratio. These irregular (aberrant) segregations are usually attributed to gene conversion involving hybrid DNA formation at the heterozygous site, with or without enzymatic correction of the resulting base mispairs. If the frequency and direction (to + and to m) of correction depend on the chemical nature of the mispair, then the chemical origin of the mutation involved in the mispair could affect its conversion spectrum, providing evidence in favour of hybrid DNA recombination models.