MAPPING OF A GENE FOR NONSPECIFIC X-LINKED MENTAL-RETARDATION - EVIDENCE FOR LINKAGE TO CHROMOSOMAL REGION XP21.1-XP22.3

Linkage analysis of a non-specific form of X linked mental retardation (MRX) was performed with 16 polymorphic markers spanning the entire X chromosome in a three generation Italian family, including four male patients with moderate mental retardation. One obligate carrier woman had mild mental retardation and another two had normal intelligence. T he results indicate tight linkage to DNA markers DXS84 (L754), DXS164 (pERT87-15), and DXS278 (CRI-S232). A maximum lod score of 2.11 at the ta = 0.00 was obtained with DXS164 and DXS278. The linked region spann ed chromosomal bands Xp21.1-Xp22.3, that is, the same portion of the X chromosome where MRX2 and MRX10-13 have been previously localised.