Final answer:
The regions at the ends of eukaryotic chromosomes are known as telomeres, which are composed of repetitive noncoding sequences that protect the chromosome.
Step-by-step explanation:
Telomeres, situated at the ends of eukaryotic chromosomes, serve a crucial role in maintaining genomic integrity. Comprising noncoding repetitive sequences, telomeres protect chromosomes from deterioration and fusion during cellular division. As cells replicate, telomeres gradually shorten, serving as a potential marker for cellular aging. To counteract this shortening, an enzyme called telomerase plays a pivotal role. Telomerase adds nucleotide sequences to the telomeres, preventing their progressive attrition. This enzymatic activity is particularly significant in cells with high proliferative capacity, such as stem cells and certain cancer cells, highlighting its relevance in cellular longevity and the broader context of health and disease.