What is the limit on the number of times a human cell can divide, typically about 50 divisions?

What is the limit on the number of times a human cell can divide, typically about 50 divisions?

• A. Genetic clock
• B. Cellular aging
• C. Hayflick limit
• D. Changes in brain functioning

Answer: (C)

The main idea here is the replicative limit of normal cells, known as the Hayflick limit. Normal human somatic cells can only divide a finite number of times—about 40 to 60 divisions in culture—before they enter a state of senescence and stop dividing. This limit exists because each cell division shortens the telomeres, the protective ends of chromosomes. When telomeres reach a critically short length, the cell detects genomic instability and halts division to prevent potential errors, effectively enforcing a cap on how many times the cell can replicate. Some cells, like germ cells, stem cells, and many cancer cells, can extend telomeres with the enzyme telomerase, which is why they can divide beyond the typical limit. The other terms don’t capture this specific, countable boundary. A genetic clock isn’t a precise concept tied to a fixed number of divisions, and cellular aging describes the broader process of aging at the cellular level rather than the exact dividing limit. Changes in brain functioning are not describing a universal cap on cell replication.

The main idea here is the replicative limit of normal cells, known as the Hayflick limit. Normal human somatic cells can only divide a finite number of times—about 40 to 60 divisions in culture—before they enter a state of senescence and stop dividing. This limit exists because each cell division shortens the telomeres, the protective ends of chromosomes. When telomeres reach a critically short length, the cell detects genomic instability and halts division to prevent potential errors, effectively enforcing a cap on how many times the cell can replicate. Some cells, like germ cells, stem cells, and many cancer cells, can extend telomeres with the enzyme telomerase, which is why they can divide beyond the typical limit.

The other terms don’t capture this specific, countable boundary. A genetic clock isn’t a precise concept tied to a fixed number of divisions, and cellular aging describes the broader process of aging at the cellular level rather than the exact dividing limit. Changes in brain functioning are not describing a universal cap on cell replication.