Final answer:
The end-replication problem is solved by the enzyme telomerase, which extends the telomeres of chromosomes to prevent DNA loss during replication.
Step-by-step explanation:
The end-replication problem is solved by the enzyme telomerase. In eukaryotic cells, DNA polymerases cannot replicate the very ends of linear chromosomes, which leads to the gradual shortening of chromosomes with each round of DNA replication. Telomerase adds sequences to the ends of chromosomes, known as telomeres, to prevent the loss of important DNA sequences. Using an RNA component as a template, telomerase extends the 3' end of the chromosomal DNA, which allows a primer to be added and the lagging strand to be completed by DNA polymerase. This critical function of telomerase helps maintain chromosome integrity and is especially important in cells with high rates of division, such as germ cells and adult stem cells.