In Fig. 4, it can be inferred that GGM and GF, who are not genotyped, both carry the haplotype shared by R1-R3 and P1-P2. In general, a haplotype can be imputed into an untyped proband if two genotyped relatives share a long haplotype IBD and the genealogy indicates that the path of IBD sharing goes through the proband. Standard conditions for that are: One of the chip-typed relatives is a descendant, preferably a child or a grandchild.With some exceptions (see 3), the other chip-typed relative should not be a descendant. Unless the mate of the proband is chip-typed, this relative is preferably substantially more closely related to the proband than the mate.The other genotyped relative could also be a descendant if either the mate of the proband is genotyped, or the two chip-typed descendants are from different mates (e.g. half-sibs).
