Fragile X and other trinucleotide repeat diseases.
Hereditary unstable DNA is composed of strings of trinucleotide repeats, in which three nucleotides are repeated over and over (ie CAGCAGCAGCAG). These repeats are found in several sites within genes; depending on their location, the number of triplet repeats in a string can change as it is passed on to offspring. When the number of repeats increases to a critical size, it can have a variety of affects on gene function. The repeats may cause a loss in gene function (as in Fragile X) or may result in the gain of a new, abnormal protein and thus a new function (as in myotonic dystrophy and Huntington disease). Although a variety of trinucleotide repeat diseases have been reported and merit consideration, this discussion will focus primarily on Fragile X syndrome, myotonic dystrophy, and Huntington disease.
The University of Alabama at Birmingham, Department of Obstetrics and Gynecology, 35249-7333, USA. kwenst@uab.edu
Katharine D
KD
Wenstrom
D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000517:prevention & control; D005820:Genetic Testing / Q000379:methods*; D006579:Heterozygote; D006801:Humans; D006816:Huntington Disease / Q000175:diagnosis / Q000235:genetics*; D008967:Molecular Biology; D009223:Myotonic Dystrophy / Q000175:diagnosis / Q000235:genetics*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods; D012680:Sensitivity and Specificity; D018911:Trinucleotide Repeats / Q000235:genetics*