Final answer:
Telomeres are the ends of chromosomes that contain noncoding repetitive sequences, protected from loss during DNA replication by the enzyme telomerase. Without telomerase, telomeres shorten over time, potentially contributing to the aging process.
Step-by-step explanation:
DNA at the ends of chromosomes, called telomeres, is not fully copied by DNA polymerase and is progressively lost with each mitotic cycle, which may correlate with the aging process. Telomeres, consisting of noncoding repetitive sequences, protect coding sequences from being lost as cells divide.
In humans, a six base pair sequence, TTAGGG, is repeated between 100 to 1000 times, forming the telomere structure. The discovery of the enzyme telomerase has clarified our understanding of how the ends of chromosomes are maintained, especially in cells like germ cells and adult stem cells, where telomerase is active.
The enzyme contains a catalytic part and a built-in RNA template, which helps elongate the telomeric DNA, allowing DNA polymerase to complete DNA replication without losing important genetic information. Without sufficient telomerase activity, as seen in most adult somatic cells, the telomeres shorten with every division, which is associated with the aging process and may contribute to cellular aging and dysfunction.