Telomerase is an enzyme that helps maintain the length of telomeres, which are protective caps at the ends of chromosomes. As cells divide, telomeres shorten, which can lead to aging and cell death. Telomerase adds repetitive nucleotide sequences to the telomeres, allowing cells to divide without losing important genetic information. This enzyme is particularly active in certain cells, such as stem cells and cancer cells. In normal somatic cells, telomerase activity is low or absent, contributing to the aging process. However, in many cancer cells, telomerase is reactivated, enabling them to divide indefinitely and contribute to tumor growth.