What happens to telomeres during successive cell divisions in somatic cells?

• A. Telomeres extend
• B. Telomeres remain unchanged
• C. Telomeres double
• D. Telomeres shorten

Answer: (D)

Telomeres are protective caps at the ends of chromosomes that prevent essential genetic information from being lost during replication. In most somatic cells, the enzyme that could extend telomeres—telomerase—is not active, so each round of DNA replication cannot fully copy the chromosome ends. This end-replication problem causes a small amount of telomere shortening with every cell division. Over many divisions, the telomeres become critically short, leading to cellular aging and eventual senescence or apoptosis. Since somatic cells don’t replenish telomeres efficiently, the net result across successive divisions is telomere shortening.