In many cancers, the cancerous cells have fully active telomerase enzymes. Explain how this might play a role in
enabling cancer cells to keep rapidly dividing.
What will be an ideal response?
ANSWER: Cancer cells are characterized by their ability to divide uncontrollably with no apparent limit
to the number of generations they can produce. Active telomerase would appear to play a key
role in allowing cancer cells to do this. During each round of DNA replication, part of the
ends of chromosomes cannot be replicated. Thus, with each cell generation, a cell loses some
of its DNA. Active telomerase places new telomere repeats at the ends of chromosomes so
that the DNA that is lost will be from telomere repeats rather than from critical genes. For
most cells, telomerase is not active, and this places a natural limit on how many replications can be performed before the cell loses critical genetic information and is unable to continue
replicating and dividing. Cancer cells with active telomerase are able to override this natural
limit on cell replication.
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