Figure 1.

Segregation of markers in an F₂ mapping family. (a) The segregation of two markers demonstrating assignment of an F₂ locus to a linkage group by the forbidden recombinant method. Two loci are shown: A, inherited as a female-informative locus and corresponding to the chromosome print for this linkage group, and B, a locus that shows a fixed difference between the two parental strains and is inherited as an F₂ marker in a 3:1 ratio of band present:band absent in the mapping family. The AFLP banding pattern for the two markers alongside each diploid genotype is shown. Occurrence of forbidden recombinant genotypes, in which both bands are absent, would indicate that the two markers are not syntenic. These genotypes would be expected to occur in one-eighth of the F₂ family for unlinked markers. The offspring shown in the box are those that are rescored as missing data for analysis of the recombination map. (b) In more detail, the problem of linkage analysis between dominant markers inherited in repulsion, demonstrated here by loci B and D. Locus C is a male-informative marker that can be used to link B and D into a single map. The first group of progeny, a–f, are informative with respect to linkage of B and C, with c and d being the recombinant genotypes. The second group, g–l, are informative with respect to linkage of C and D. Note that because of dominance, a–f are uninformative with respect to locus D, and g–l are uninformative with respect to locus B.