A researcher has identified a gene linked to a neurodegenerative disease. In individuals that suffer symptoms of this disease, at a specific location within this gene the sequence CAG is repeated many times more than it is in unaffected individuals. This disease exemplifies the phenomenon of .

Expanding triplet repeats

Explanation:

Expanding triplet repeats causes a disorder called Triple repeat disorder. It’s a genetic and dominantly inherited neurological disorder and is also classified as an unstable mutation.

Most of these disorders involve a CAG·CTG repeat expansion, such as Huntington disease etc.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).