What happens to telomeres as cells divide?

Telomeres are repetitive DNA sequences located at the ends of chromosomes, and their primary function is to protect chromosome ends from degradation and prevent them from fusing with one another. As cells undergo division, particularly during mitosis, a phenomenon known as the "end replication problem" occurs. This leads to the progressive shortening of telomeres with each round of cell division.

Once a threshold length is reached, the cell may enter a state known as senescence, where it stops dividing, or it may undergo apoptosis (programmed cell death). This mechanism serves as a natural limit on the number of times a cell can divide, playing a significant role in aging and the potential development of cancer. Cells with severely shortened telomeres can also be prone to genomic instability, which is a characteristic feature of cancerous cells.

In summary, the correct answer reflects the biological reality that telomeres shorten with consecutive cell divisions, thereby limiting the number of times a cell can successfully replicate and maintain its genomic integrity.