Why do HeLa cells never die?

• A. They are immune to DNA damage
• B. They never divide
• C. They rapidly die in culture
• D. They have an active telomerase that prevents telomere shortening

Answer: (D)

The key idea is that keeping the ends of chromosomes intact allows cells to keep dividing. Each time a cell divides, telomeres at the chromosome ends shorten a little. When they get too short, the cell stops dividing or dies. HeLa cells avoid this fate because they have active telomerase, the enzyme that adds DNA repeats to telomeres and renews their length. In most adult cells, telomerase is off, so telomeres shorten with each division and the cells eventually enter senescence. Cancer cells like HeLa often reactivate telomerase, so their telomeres are maintained and they can keep dividing in culture for many generations. So their longevity isn’t about being immune to damage or never dividing—it’s about telomerase preserving their chromosome ends and enabling ongoing replication.