Early Generation Analysis of Lengths of Heterozygous Chromosome Segments around a Locus Held Heterozygous with Backcrossing or Selfing.

HEN a locus is held heterozygous for n generations of backcrossing, the W average length of heterozygous segments surrounding the selected locus asymptotically approaches 2Jn (FISHER 1949). With the equivalence of eight to ten generations of backcrossing this criterion is adequate. Experiments which involve early generation tests with genetically similar or “isogenic lines”, chromosome substitution studies, factor transfer or the development of genetic stocks require a more exact criterion for heterozygous segment lengths for the early generations of inbreeding. The objective of this paper is to develop a distribution of the segment lengths heterozygous about a locus held heterozygous for any number of generations of backcrossing or selfing.