Linkage studies in affected sib pairs

There are problems applying the lod score method to complex traits, and a common alternative is to examine marker allele-sharing between pairs of affected relatives, for example using the sib-pair method.

The second sib pair shares one allele IBD, while all the others share both alleles, suggesting a recessive gene may be quite closely linked to the marker.

If relative pairs share marker alleles more often than would be expected by chance, this suggests that a susceptibility locus may be linked to the marker.