Final answer:
In eukaryotes, linear chromosomes create an end replication problem due to the absence of a primer at the end of the chromosome. However, telomeres, repetitive sequences at the ends of chromosomes, help solve this problem by being replicated by the enzyme telomerase and ensuring that the ends of the chromosomes are replicated.
Step-by-step explanation:
Unlike prokaryotic chromosomes, eukaryotic chromosomes are linear. The enzyme DNA pol can add nucleotides in the 5' to 3' direction. In the leading strand, synthesis continues until the end of the chromosome is reached. On the lagging strand, DNA is synthesized in short stretches, each initiated by a separate primer. However, when the replication fork reaches the end of the linear chromosome, there is no place for a primer to be made for the DNA fragment at the end. Over time, these ends may get progressively shorter as cells continue to divide.
Telomeres, the repetitive sequences at the ends of linear chromosomes, play a crucial role in solving this problem. These telomeres are replicated by an enzyme called telomerase, which adds complementary bases to the RNA template and extends the lagging strand template. Once the template is sufficiently elongated, DNA polymerase can add nucleotides to complete replication. This ensures that the ends of the chromosomes are replicated, preventing them from getting progressively shorter with each round of DNA replication.