Final answer:
In circular DNA replication, the problem arises when there is no available strand for a primer at the end of the lagging strand, leading to progressively shorter chromosomes. This is resolved by the enzyme telomerase, which extends the strand allowing for complete replication and preserving the telomeres.
Step-by-step explanation:
The issue at the end of the lagging strand synthesis during circular DNA replication arises because DNA polymerase can only add nucleotides in the 5' to 3' direction. The Okazaki fragments generated on the lagging strand require primers, which are eventually removed. When the replication fork reaches the very end of the linear chromosome, there's no upstream DNA where a new RNA primer can be laid down for the completion of the lagging strand. As a result, a piece of DNA at the end of the chromosome is left unreplicated, leading to progressively shorter chromosomes with each round of cell division. However, this problem is resolved by the enzyme telomerase, which extends one of the strands, providing a template for the lagging strand to be completed, thus ensuring that chromosome ends, or telomeres, are maintained and not genes that are crucial for cell survival and function.