Final answer:
Telomerase is an enzyme that maintains the integrity of linear chromosomes by adding telomeres. It is active in germ cells, adult stem cells, and certain cancer cells. Telomerase prevents chromosomes from shortening during replication and ensures genetic stability.
Step-by-step explanation:
Telomerase plays a critical role in maintaining the integrity of linear chromosomes. It is typically active in germ cells, adult stem cells, and some cancer cells. Telomerase adds short repetitive sequences called telomeres to the ends of chromosomes to prevent them from shortening during replication. This allows cells to divide and proliferate without damaging genetic material. Telomerase is present in these cells in order to maintain the length of telomeres and ensure the stability of chromosomes. However, telomerase is not active in adult somatic cells, which are the majority of cells in the body.