How many X-linked genes for non-specific mental retardation (MRX) are there?
- and others
X-linked mental retardation (XLMR) is that proportion of mental retardation (MR) showing the distinctive pattern of inheritance associated with the X chromosome. XLMR is subdivided into syndromal and non-specific (MRX) forms. MRX is clinically homogeneous but genetically heterogeneous. Affected males in families segregating MRX have no consistent phenotypic expression apart from their MR to distinguish them from unaffected males or affected males in other MRX families. Syndromal MRs have additional neurological or phenotypic characteristics that define a syndrome, and most of these syndromes are rare. Within some families an affected male may show {open_quotes}soft{close_quotes} syndromal signs, but where this is not evident in other affected males from the same family, the MR is diagnosed as non-specific. Delineation from fragile X syndrome or FRAXE MR can now be confidently made with the aid of direct molecular tests which detect the (CCG){sub n} expansion at either FRAXA or FRAXE. MRX can be expressed in carrier females but with milder manifestations. The gene in such cases could be partially dominant or result from a skewed X-inactivation pattern in neural tissue. 39 refs., 1 fig., 1 tab.
- OSTI ID:
- 476926
- Journal Information:
- American Journal of Medical Genetics, Vol. 64, Issue 1; Other Information: PBD: 12 Jul 1996
- Country of Publication:
- United States
- Language:
- English
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BASIC STUDIES
HUMAN X CHROMOSOME
GENETIC MAPPING
CHROMOSOMAL ABERRATIONS
MEIOSIS
RESOLUTION
REVIEWS
MENTAL DISORDERS
GENETICS
MALES
HEREDITARY DISEASES
PHENOTYPE
GENES
GENE RECOMBINATION
GENE MUTATIONS
DNA-CLONING
DNA SEQUENCING
POLYMERASE CHAIN REACTION
STATISTICS
BIOLOGICAL MARKERS
NUCLEOTIDES