Nail-patella syndrome--a preliminary study for genetic linkage with ABO blood group.

Linkage means a very close association between two adjacent genes, so much so that no crossing-over occurs between them and they are always transmitted together to the next generation, provided there is no mutation. The linkage between nail-patella gene and ABO blood group gene, located on the 9th chromosome, shows the same. This can be understood from the pedigree analysis of an affected family, which is the first step in studying the molecular pathology of the diseased gene.