Figure 3.

RIL construction. Conventional RILs are generated by crossing two inbred lines (P₀), each here represented by a single pair of homologous chromosomes. The cross yields F₁s that are heterozygous at every locus that differs between the strains. Self-fertilization of F₁ hermaphrodites yields genetically heterogeneous F₂s. Because of complete crossover interference in C. elegans, each F₂ carries on average one recombinant chromosome with a single crossover. Each F₂ is independently inbred by selfing until the F₁₀ generation, at which point the genome is expected to be completely homozygous, with an average of one crossover per chromosome. This collection of homozygous strains is a panel of RILs. Note that this panel will all inherit the mitochondrial genome of the P₀ hermaphrodite. To balance the panel with respect to mitochondrial genotype, an equal number of RILs should be constructed from the reciprocal cross.