Maternal FMR1 premutation allele expansion and contraction in fraternal twins.

Fragile X syndrome results from an expansion of the CGG trinucleotide repeat in the 5' untranslated region of the Fragile X Mental Retardation 1 (FMR1) gene. Expansion of a maternal premutation allele is the mechanism by which a full mutation allele arises; contraction of a maternal premutation allele is rare. Here we report on both an expansion and contraction of a maternal FMR1 premutation allele in fraternal twins.

Genetic approach to evaluation of hearing loss.

Information on the genetic basis of and testing for disorders with hearing loss is increasing rapidly. In this review, the authors explain genetic terminology, the principles of inheritance, and the types of genetic variation and the genetic basis of selected disorders of hearing loss. The authors also review how information on genetics and genetic testing can be obtained, outline a genetic approach to the diagnosis of hearing loss, and discuss how otologists and geneticists can work together to strengthen the clinical applications of genetics to individuals and families who have hearing loss.

Recurrent distal 7q11.23 deletion including HIP1 and YWHAG identified in patients with intellectual disabilities, epilepsy, and neurobehavioral problems.

We report 26 individuals from ten unrelated families who exhibit variable expression and/or incomplete penetrance of epilepsy, learning difficulties, intellectual disabilities, and/or neurobehavioral abnormalities as a result of a heterozygous microdeletion distally adjacent to the Williams-Beuren syndrome region on chromosome 7q11.23. In six families with a common recurrent ∼1.