What are the structures at the ends of eukaryotic chromosomes that protect them from deterioration?

The structures at the ends of eukaryotic chromosomes that protect them from deterioration are known as telomeres. Telomeres consist of repetitive nucleotide sequences that do not encode genes but serve an essential role in maintaining the stability and integrity of chromosomes. Each time a cell divides, the telomeres shorten, which eventually leads to cellular aging and limits the number of times a cell can divide, a phenomenon known as the hayflick limit. This protective function prevents the loss of essential genetic information during DNA replication, as the telomeres act as buffers against the loss of coding sequences.

In contrast, centromeres play a different role as they are the regions of a chromosome where the two sister chromatids are held together and are essential during cell division for the correct segregation of chromosomes. Histones are proteins that help package DNA into a compact form known as chromatin, which aids in the organization and regulation of gene expression, but they do not specifically protect chromosome ends. Chromatin refers to the complex of DNA and histone proteins that form chromosomes, highlighting the structural organization of genetic material rather than its terminal protection functions.