MAXIMUM-LIKELIHOOD MODELS FOR MAPPING GENETIC-MARKERS SHOWING SEGREGATION DISTORTION .2. F2 POPULATIONS

In F-2 populations, gametic and zygotic selection may affect the analy sis of linkage in different ways. Therefore, specific likelihood equat ions have to be developed for each case, including dominant and codomi nant markers. The asymptotic bias of the ''classical'' estimates are d erived for each case, in order to compare them with the standard error s of the suggested estimates. We discuss the utility and the efficienc y of a previous model developed for dominant markers. We show that dom inant markers provide very poor information in the case of segregation distortion and, therefore, should be used with circumspection. On the other hand, the estimation of recombination fractions between codomin ant markers is less affected by selection than is that for dominant ma rkers. We also discuss the analysis of linkage between dominant and co dominant markers.