Identification of the Gene Responsible for Adenomatous Polyposis 
particular mutation has been characterized in a 
family, members who carry the disease allele can 
be identified directly. Families for whom the mu- 
tant allele is as yet unidentified may still benefit 
from analysis of genetic linkage between the pu- 
tative disease allele and a highly polymorphic 
DNA marker system that has been detected within 
one of the other genes lying in the APC deletion 
region. Early diagnosis at the molecular level will 
free unaffected members of these families from 
some anxiety and spare them the discomfort and 
expense of frequent colonoscopic examinations. 
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