Telomere repeats and the DNA damage response. Telomeres have very specific sequences of repeats along their length, and at least 12 TTAGGG repeats and their associated proteins are required for the telomere to execute its primary function. If there are insufficient repeats, the telomere looks like a double-strand break. Such an “uncapped” telomere will activate a DNA damage response involving the Ataxia-Telangiectasia mutated (ATM) kinase and p53.