However, telomerase activity is repressed in most human somatic cells around the time of birth, so telomerase activity remains sufficient to maintain telomere length only in highly proliferative populations, including germline and stem cells, and the vast majority of cancer cells in which mutations in the TERT promoter region or alternative splicing of the TERT transcript endow them with unlimited replicative potential (Kim et al. 1994; Batista 2014; Dratwa et al. 2020; Penev et al. 2021; Cong et al. 2002). The gene discussed is TERT; the disease is cancer.