[Formation of pedigrees for recombinational analysis of recessive traits]

The efficiency of different methods of the directed extension of the pedigrees that are used to analyze the linkage of recessive genes was studied. It was demonstrated that the addition of parents' relatives with abnormal phenotypes into the pedigree allowed the total sample size to be considerably decreased. All other methods of pedigree extension are efficient only when they take into account the phenotypes of the added relatives: at least one relative should have an abnormality. The generally accepted notion that three-generation pedigrees are optimal for linkage analysis was disproved for the case of recessive abnormal traits. A choice between two alternatives for construction of pedigree samples was discussed: (1) the use of only nuclear pedigrees strictly tested for informative value with respect to linkage analysis and (2) the introduction of any nuclear pedigree carrying an abnormality into the sample and the subsequent extension of the pedigree.