Abstract

Variations in DNA sequence generate polymorphisms which can be followed through families. A cloned gene specific probe for human complement 3 (C3) was hybridised to DNA samples digested with restriction endonucleases. The C3 probe detects several restriction fragment length polymorphisms (RFLPs) that occur frequently in the general population. These DNA alleles can be readily used in linkage analyses of loci on chromosome 19, since most families studied are informative. The inheritance of one such polymorphism was followed through myotonic dystrophy families. The segregation data for both the C3 protein polymorphism and the C3 RFLP support the linkage of myotonic dystrophy (DM) and C3.