Telomeres are repetitive DNA sequences located at the ends of linear chromosomes. They serve as protective caps that prevent chromosome ends from fraying, sticking to each other, or being mistaken for broken DNA strands by the cell's repair machinery

. In humans, the telomere sequence is typically the repeat TTAGGG, repeated thousands of times

. Each time a cell divides, the telomeres become slightly shorter because DNA replication cannot fully copy the very ends of chromosomes. When telomeres become too short, the cell can no longer divide and eventually dies, which contributes to cellular aging

. To counteract this shortening, some cells use an enzyme called telomerase to add back telomere sequences and maintain their length, especially in germ cells, stem cells, and certain white blood cells

. Telomeres also form a looped structure called a T-loop, stabilized by specific proteins, which helps protect chromosome ends and maintain genome stability

. This protective role of telomeres is crucial for normal cell division and preventing genomic instability, which can lead to cancer if cells divide uncontrollably beyond the telomere limit

. In summary, telomeres are essential DNA-protein structures at chromosome ends that protect genetic information, regulate cellular lifespan, and maintain chromosome integrity during cell division