The process of expanding the new DNA strands continues until there is either no more DNA template left to replicate (i.e. at the end of the chromosome), or two replication forks meet.
The meeting of two replication forks is not regulated and happens randomly along the course of the chromosome.
Once DNA synthesis has finished, it is important that the newly synthesised strands are bound and stabilized.
Two enzymes are needed to achieve this in the lagging strand:
Flap endonuclease (FEN) removes the RNA primer that is at the beginning of each Okazaki fragment.
DNA Ligase joins fragments together to create one complete strand.
Every RNA primer synthesized during replication can be removed and replaced with DNA strands except the RNA primer at the 5′ end of the newly synthesized strand.
This causes both daughter DNA strands to have an incomplete 5′ strand with 3′ overhang.
In the absence of additional cellular processes, exonucleases would digest (i.e remove) these single-stranded 3′ overhangs.
Thus each daughter DNA would become shorter than the parental DNA which will gradually shorten the chromosomes.
To prevent this shortening, the ends of linear eukaryotic chromosomes have special structures of repeated DNA sequences called telomeres.
