I am using three intragenic FVIII polymorphisms (SNP) ( intron18 BCL1 T>A , intron 19 HindIII C>T, and IVS7 nt27 G>A) for indirect linkage analysis for carrier detection in hemophilia A families , my question is that how we can determine the informativity of the marker in each family ? beside the need for heterozygosity of the mothers what else we need?