The gene responsible for nonsyndromic mental retardation in a family w
ith 7 affected males has been localized to Xp21. The maximal two-point
lod score was 3.31 for tight linkage to marker DXS1202 in Xp21.3-p22.
3 with crossovers between the 3' portion of the DMD gene (DXS1234) pro
ximally and locus DXS989 distally. The XLMR gene in this family has be
en assigned the designation MRX29. The localization overlaps with at l
east six other MRX entities Linked to the distal short arm of the X ch
romosome.