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CAG Repeat

Meaning

A CAG repeat is a segment of DNA characterized by multiple, consecutive repetitions of the cytosine-adenine-guanine trinucleotide sequence. This specific genetic motif codes for the amino acid glutamine, and an excessive number of these repeats can lead to the production of an abnormally long polyglutamine tract within a protein. In clinical genetics, the number of these repeats is crucial because an expansion beyond a certain threshold is associated with a group of inherited neurodegenerative disorders. The length of the CAG repeat often correlates inversely with the age of disease onset and severity.