At this rate, after 125 mitotic divisions, the telomeres would be completely gone. Telomeres and Cellular Aging Telomeres are important so their steady shrinking with each mitosis might impose a finite life span on cells. This, in fact, is the case. See Cancer Cells in Culture for a discussion of the differences between normal and cancerous cells grown in culture. Cells removed from a newborn infant and placed in culture will go on to divide almost 100 times.
Some cells are immortal.
It turns out that these cells are able to maintain the length of their telomeres. They do so with the aid of an enzyme telomerase . Telomerase Telomerase is an enzyme that adds telomere repeat sequences to the 5' end of DNA strands. By lengthening the strand prior to replication, cells with active telomerase are able to compensate for telomere shortening during DNA replication. However, when normal somatic cells are transformed in the laboratory with DNA expressing telomerase, they continue to divide by mitosis long after their normal life span is over.