SHADOW BANDS SEEN WHEN TYPING POLYMORPHIC DINUCLEOTIDE REPEATS - SOMECAUSES AND CURES

Polymorphic dinucleotide repeats are generally typed by using the PCR to generate products that are resolved on denaturing acrylamide gels. The presence of ''shadow bands'' on these gels often makes it difficul t to score alleles reliably. We have developed procedures that overcom e many of these difficulties. Important aspects of these improved proc edures include using gels containing formamide as well as urea, transf erring the resolved allelic fragments to nylon membranes by capillary blotting and probing the membranes with locus-specific oligonucleotide probes.