Anticipation is common in trinucleotide repeat disorders, such as Huntington's disease and myotonic dystrophy, where a dynamic mutation in DNA occurs.
This is the case for Huntington's disease, where the trinucleotide repeat encodes a long stretch of glutamine residues.
[citation needed] In order to have a deleterious effect, the number of repeats must cross a certain threshold.
For example, normal individuals have between 5 and 30 CTG repeats within the 3' UTR of DMPK, the gene that is altered in myotonic dystrophy.
However, meiotic instability could result in a dynamic mutation that increases the number of repeats in offspring inheriting the mutant allele.