Semiconservative synthesis of the leading strand in a linear chromosome
can proceeds normally to the end of the double helix.
On the lagging strand, after the last RNA primer is removed, there is no free 3'-OH for DNA polymerase to elongate.
The gap on the lagging strand leads to shortening of the chromosome after each round of synthesis.
This chromosome shortening may play a role aging of somatic cells,
and must be avoided in germ cells.