Figure 2 : Genetically engineered CRs reduce meiotic fitness.

From: Genome architecture is a selectable trait that can be maintained by antagonistic pleiotropy

Figure 2

(a) Schematic representation of karyotypes for 10 different genetically engineered S. pombe strains. All the strains are isogenic except for the rearrangement and its breakpoint. Chromosomes are drawn to scale. Inflexions represent the centromeres. To generate the CR strains, Cre recombinase was expressed in parental strains using a plasmid and selecting for two colonies, each representing a totally independent recombination event. (b) Meiotic viability of homozygotic and heterozygotic crosses. CRs reduce meiotic viability in heterozygotic crosses from 8 to 48% with the exception of T8 that exhibits no apparent reduction. Meiotic viability corresponds to the number of viable haploid spores that have formed a colony divided by the total number of spores. Each cross represents the analysis of 18–63 tetrads. Error bars represent 2 × s.e. for a binomial distribution. P—parental strain; R—rearranged strain. (c) Frequency of recombination between loci at the breakpoints and the mat1 locus. Inversions suppress recombination between any of the breakpoints and the mat1 locus by ~30%. In contrast, translocations do not significantly reduce recombination frequency. Only rearrangements involving chromosome II were scored. Error bars correspond to 2 × s.e. for a binomial distribution.