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Telomerase Function
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Will chromosomes remain stable of over very long periods of time? Each round of genetic replication followed by mitosis or meiosis requires the replication of a complete version of each chromosome. Any accidental changes in chromosome structure will be permanent. These changes will be passed on through future rounds of DNA replication. Therefore any loss of DNA is a serious problem. If the end of a DNA strand is not copied each time the DNA is replicated then the chromosome will shrink continuously as the cell cycle continues. Because errors persist and accumulate over time it is very important to prevent the accumulation of DNA damage and loss.

Telomerase is an enzyme that adds repetitive DNA sequences to the 3’ ends of DNA on eukaryotic chromosomes. Telomerase is only expressed in cells that need to divide regularly, such as embryonic stem cells and certain cells of the immune system. Telomerase is not typically expressed in most somatic cells.

View the animation below, then complete the quiz to test your knowledge of the concept.





1DNA polymerases cannot replicate
A)the 5’ end of circular chromosomes.
B)the 3’ end of circular chromosomes.
C)the 5’ end of linear chromosomes.
D)the 3’ end of linear chromosomes.
E)both the 5’ and 3’ ends of linear chromosomes.


2Telomerase is unique because it contains
A)a DNA molecule.
B)an RNA molecule.
C)different RNA molecules.
D)different DNA molecules.
E)both DNA and RNA molecules.


3Which of the following best describes the function of telomerase at the telomere?
A)It makes special primers that do not need to be removed.
B)It synthesizes new DNA without the use of a template.
C)It adds new DNA to both strands of the telomere overhang.
D)It adds new DNA to the shorter strand of the telomere overhang.
E)It adds new DNA to the longer strand of the telomere overhang.


4Telomeres consist of direct repeat sequences.
A)True
B)False


5In the absence of telomerase activity, chromosomes are shortened slightly after every round of replication.
A)True
B)False





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