trinucleotide repeat

(try-NOO-klee-oh-tide reh-PEET)

Sequences of 3 nucleotides repeated in tandem on the same contiguous section of chromosome. A certain amount of normal (polymorphic) variation in repeat number with no clinical significance commonly occurs between individuals; however, repeat numbers over a certain threshold can, in some cases, lead to adverse effects on the function of the gene, resulting in genetic disease.

Pronunciation of dictionary term "trinucleotide repeat"