Final answer:
Telomeres are extended by the enzyme telomerase, which allows DNA polymerase to complete chromosome replication, maintaining chromosome integrity.
Step-by-step explanation:
Eukaryotic cells have linear chromosomes that present a unique challenge during DNA replication, particularly at their ends known as telomeres. Telomere replication involves a specialized enzyme called telomerase, which adds repetitive nucleotide sequences to the ends of chromosomes. With the help of an inbuilt RNA template, telomerase extends the 3' end of the chromosome, allowing DNA polymerase to complete synthesis by adding complementary nucleotides. This mechanism is essential for maintaining chromosome integrity during cell division and is especially active in germ cells and stem cells.