Two were detected because they were homozygous for a cystic fibrosis mutation for which only the mother was heterozygous, and one because he was homozygous for a rare COL1A2 mutation.
Genetic linkage has been analyzed between cystic fibrosis (CF) and a number of markers on the long arm of chromosome 7, including D7S15, COL1A2, PON, MET, D7S8, and TCRB, using a cohort of 47 Canadian and 13 Danish CF families.
The results of the two-point and three-point linkage analyses indicate that the most probable order of these four genetic loci is COL1A2-D7S15 - PON - CF.
The linkage of cystic fibrosis (CF) and the polymorphic DNA markers pJ3.11, met, 7C22, DOCR1-917, COL1A2, and TCRB have jointly localized the mutation causing CF to chromosome 7q2.1-3.1.