CAGTrinukleotidRepeats

CAGTrinucleotideRepeats are segments of DNA where the sequence "CAG" is repeated consecutively multiple times. These repeats are found in various genes within the human genome and in other organisms. The number of CAG repeats can vary significantly between individuals and can also change over time. When these repeats occur in a gene, they can lead to the production of a protein with an expanded polyglutamine tract, which is a stretch of the amino acid glutamine.

The clinical significance of CAG trinucleotide repeats lies in their association with a group of neurodegenerative disorders known as polyglutamine diseases. These diseases include Huntington's disease, spinocerebellar ataxias (types 1, 2, 3, 6, 7, and 17), and dentatorubral-pallidoluysian atrophy. In these conditions, an abnormally high number of CAG repeats within the coding region of a specific gene leads to the misfolding and aggregation of the resulting polyglutamine protein. This accumulation of aberrant proteins in brain cells is believed to cause cellular dysfunction and eventual neuronal death, leading to the characteristic symptoms of these diseases. The severity and age of onset of these disorders are often correlated with the number of CAG repeats, with longer repeat expansions generally resulting in earlier onset and more severe phenotypes. Genetic testing can determine the number of CAG repeats in individuals suspected of having or carrying the predisposition for these disorders.