What are telomeres?

Telomeres are stretches of repetitive DNA found at the ends of chromosomes. Their primary function is to protect the chromosome from deterioration or from fusion with neighboring chromosomes, which can lead to genetic instability. Each time a cell divides, a portion of the telomere is lost due to the nature of DNA replication, which is why telomeres are crucial for cellular aging and limiting the number of times a cell can divide. They act as protective caps that prevent the loss of important genetic information during cell division.

In contrast, other options refer to different structures or components. For example, segments of RNA at the start of chromosomes or proteins that stabilize chromosome structure do not encompass the core definition and function of telomeres. Additionally, enzymes related to DNA replication are instrumental in the process but do not describe the protective, repetitive DNA sequences found at the ends of chromosomes. Thus, understanding telomeres as DNA stretches illuminates their role in cellular biology and the aging process.