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.