Replication problem at the ends of linear DNA

Since DNA is synthesized in the 5' to 3' direction
only, the two templates of the parent molecule
differ with respect to the continuity of synthesis.
On the 5' to 3' template strand, synthesis occurs
in the reverse direction relative to the fork
movement (lagging strand synthesis). There,
DNA is synthesized in short fragments about
1000–2000 nucleotides long in bacteria and
about 200 nucleotides in eukaryotes (Okazaki
fragments, see DNA replication, p. 42). However,
8–12 bases at the end of the lagging strand
template cannot be synthesized by DNA polymerase
because the primer it requires cannot be
attached beyond the end of the template strand.
Hence, at each round of replication before cell
division, these 8–12 nucleotides will be lost at
the chromosome ends. Some organisms compensate
for this loss by adding telomeric repeats
to the ends of the chromosome during the
replication cycle.