Final answer:
In yeast, Drosophila, and Arabidopsis, replication termination in eukaryotes involves complexities due to their linear chromosomes, where telomerase extends the ends to maintain chromosome integrity.
Step-by-step explanation:
Termination of DNA Replication in Eukaryotes
In eukaryotic organisms such as yeast (Saccharomyces cerevisiae), Drosophila (Drosophila melanogaster), and Arabidopsis (Arabidopsis thaliana), the process of DNA replication termination is quite complex due to the linear structure of their chromosomes. Unlike prokaryotes which have circular chromosomes, these eukaryotic organisms possess linear chromosomes that end with regions called telomeres. As DNA replication nears the end of a chromosome, the leading strand can be completed normally while issues arise with the lagging strand, which is synthesized in short fragments known as Okazaki fragments.
The removal of the RNA primer from the last Okazaki fragment at the very end of the lagging strand leaves a section of unreplicated DNA. This is because conventional DNA polymerase requires a primer to add nucleotides and cannot start synthesis de novo. As a result, the telomerase enzyme plays a critical role in adding repetitive nucleotide sequences to the ends of chromosomes, thereby preventing the shortening of DNA with each round of replication. Yeast, with its autonomously replicating sequences (ARS), exhibits similar replication dynamics as do Drosophila and Arabidopsis, with telomerase action being essential for maintaining chromosome integrity during cell division and replication.