A polymorphic site at D11S384, which shows zero recombination with the ataxia-telangiectasia (A-T) locus, was originally detected by Mutation Detection Enhancement Gel and Denaturing Gradient Gel Electrophoresis. In order to increase the throughput and decrease the complexity of the assays, we developed a site directed mutagenesis using primers with mismatched 3'ends, followed by restriction digestion, as a rapid, nonradioactive method for detecting polymorphisms/mutations. (C) 1995 Academic Press, Inc.