Question

If a patient has an abnormality in telomerase activity, how might this contribute to cancer?

Answer 1

The mitotic clock is regulated by the “telomeres” of the DNA. The telomeres contain a six base sequence repeated for several hundreds of times. With each cycle, about 1200 nucleotides are excised out, so, when a certain number of nucleotides are cut the cell division ceases. The rate of telomere shortening increases during stress, which decreases the lifespan of the cell.

The loss of nucleotides at the ends of telomeres is inhibited as the cancer cells express the enzyme, “telomerase.” Telomerase is an enzyme which adds DNA (deoxyribonucleic acid) sequence repeats, (5^’-TTAGGG-3^’ in all vertebrates) to the 3^’ ends of the DNA in the telomere regions. Telomeres are the non-coding DNA sequences present at the very ends of chromosomes. So, the ends of chromosomes can be copied, and the cancer cells avoid natural process of cell death.