INCLUSION OF SYNTHETIC DNA TEMPLATES OF SIMILAR LENGTH AND BASE COMPOSITION TO PCR-AMPLIFIED PRODUCTS IN RESTRICTION ENZYME DIGESTIONS - ANEFFICIENT AID IN CHARACTERIZATION OF POINT MUTATIONS

Because of a subtle anomaly we encountered upon an analytical gel whil e characterizing a point mutation in an exon of a patient, we decided to perform expensive and time-consuming procedures to characterize the anomaly. Although initial and subsequent Southern blots and PCR analy ses of this patient's mutation suggested that his mutation lay directl y within a TaqI recognition site, further characterization revealed th at the mutation actually lay in a base immediately outside the recogni tion site. Had we included an appropriate double-stranded DNA control in the restriction enzyme digestion of this patient's PCR-amplified ex on, we could have arrived at the correct conclusion as to the location of the mutation without incurring high costs and time loss. This brie f report depicts the use of DNA controls of appropriate length and bas e composition as a means of avoiding erroneous conclusions and expense in routine mutational analyses in the clinical setting.