premutation


Also found in: Encyclopedia.

premutation

(pre?mu-ta'shun)
A sequence of multiply repeated nucleotides that may produce a disease in one's offspring but may not produce clinically apparent disease in the carrier. A common premutation occurs in the Fragile X syndrome, in which ancestors of affected children may have 50 — 200 copies of the trinucleotide sequence CGG. These individuals do not have the full phenotypic expression of the Fragile X syndrome but as adults may suffer Parkinson-like movement disorders such as ataxia and tremors.
Synonym: intermediate allele

Premutation

A change in a gene that precedes a mutation; this change does not alter the function of the gene.
Mentioned in: Fragile X Syndrome
References in periodicals archive ?
Qualitative assessment of FMR1 (CGG)n triplet repeat status in normal, intermediate, premutation, full mutation, and mosaic carriers in both sexes: implications for fragile X syndrome carrier and newborn screening.
Many laboratories incorrectly identified samples with 42 repeats as gray-zone or premutation.
Repeat CGG sequences are categorized into four classes based on repeat length: normal (<45 repeats); intermediate (45-54 repeats); premutation (55-200 repeats); and full mutation (>200 repeats).
3% of the general female population may be premutation carriers; the prevalence of males with premutations is approximately half that.
Would parents be inclined to display confidence-eroding bias toward a child who harbors a premutation, which may carry little risk of developmental disability?
AGG Genotyping Reclassifies Expansion Risk for Equivalently Sized Intermediate and Premutation Fragile X Alleles: Outcomes of a Multicenter Study of 469 Mother-Child Transmissions" (Andrew Hadd, Asuragen; Sarah Nolin, NYS-IBR; Elizabeth Berry-Kravis, Rush; Flora Tassone, UC-Davis; Stephanie Sherman, Emory, Abstract No.
Because her FSH concentration was increased in the setting of hypoestrogenism, PCR testing of the FMR1 5' UTR identified the patient as having an FMR1 premutation allele with 82 CGG repeats and the second allele containing 51 CGG repeats (reference intervals: normal, 5-44 repeats; intermediate, 45-54; premutation, 55-200; full mutation, >200 repeats), resulting in a conclusive diagnosis of FXPOI.
Press Conference on Major Announcements Related to Premutation and Autism
Women who carry a premutation in one of their two copies of the FMR1 gene have a 13%-26% risk of developing POF.
7) On the other hand, clinical interpretation depends on the clinical context: For example, an FMR1 gene premutation is interpreted differently if the patient is a child with developmental delay, a pregnant woman, a woman having trouble becoming pregnant, or an elderly man with ataxia.
These premutations are unstable and can expand in size when passed from mother to child If the premutation expands to the size of a full mutation, the FMR-1 gene "turns off" and does not work properly.