A DNA segment D20S5 isolated from a chromosome 19/20 flow-sorted library was shown to identify two restriction fragment length polymorphisms (RFLPs) with MspI and PvuII. The probe was localized by hybridization in situ to 20p12, the putative site of an interstitial deletion in some MEN 2A and 2B patients. Linkage of the D20S5 and MEN 2A loci was excluded at theta less than or equal to .13 using two large MEN 2A kindreds. These data suggest that the MEN 2A locus may not lie within 20p12 as previously suggested.
