More than 90% of cancer cells have fully active telomerase enzymes. Explain how that might play a
role in enabling cancer cells to keep rapidly dividing.
What will be an ideal response?
Cancer cells are characterized by their ability to divide out of control and with no apparent limit to the
number of generations that they can produce. Active telomerase would appear to play a key role in
allowing cancer cells to do just that. 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 and not 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 able to replicate and divide no more. Cancer cells with active telomerase are able to
override this natural limit on cell replication.
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Isolating chromosomes during metaphase then fragmenting, denaturing, and labeling them with a unique combination of fluorescent dyes is called
A. chromosome typing. B. chromosome painting. C. karyotyping. D. DNA painting. E. None of the answer options is correct.
A and B are linked genes. In a study of 100 offspring, 94 had parental genotypes for A and B, while 6 were recombinants. A and B are ________ map units apart.
A) 4 B) 6 C) 9.4 D) 94
The competitive exclusion principle states ________.
a) two species cannot occupy the same niche in a habitat b) certain species can have disproportionately large effects relative to their abundance c) certain small areas hold unusually large number of species d) nonnative species introduced into a new ecosystem can cause native species to go extinct
The discontinuous aspect of replication of DNA in vivo is caused by ________
A) topoisomerases cutting the DNA in a random fashion B) trinucleotide repeats C) polymerase slippage D) the 5? to 3? polarity restriction E) sister-chromatid exchanges