You are asked to participate in a clinical trial for a new drug that can activate telomerase. Which of the following is a likely risk of such a drug?

Question

A.  decreased capacity for tissue repair
B.  increased vulnerability to cancer
C.  premature aging
D.  decreased telomere length

Clarify Question
  · What is the key concept addressed by the question?
· What type of thinking is required?
 · What key words does the question contain?
 
Gather Content
· What do you already know about telomeres and telomerase?
 
Consider Possibilities
· What other information is related to the question? Which information is most useful?
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?  
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  increased vulnerability to cancer

Clarify Question
  · What is the key concept addressed by the question?
    o This question addresses the function of telomerase.
 
· What type of thinking is required?
    o This answer requires you to weigh and judge evidence – to Evaluate – and choose the best of the possible answers.
 · What key words does the question contain?
    o A clinical trial is a test of a new drug using human patients. Telomerase is the enzyme that builds telomeres on the ends of DNA.
 
Gather Content
· What do you already know about telomeres and telomerase?
    o Telomeres are short repeated sequences of DNA, which are found at the tips of each chromosome.
    o They are made by an enzyme called telomerase, which uses an internal RNA as a template and not the DNA itself.
    o Telomeres serve to cap off the end of the DNA, protecting it and preventing the molecule from getting shorter in every replication (due to the usual need for a primer).
 
Consider Possibilities
· What other information is related to the question? Which information is most useful?
    o A gradual shortening of the ends of chromosomes occurs in the absence of telomerase activity. This is part of the reason cells senesce, or eventually age and die.
    o During embryonic and childhood development in humans, telomerase activity is high, but it is low in most somatic cells of the adult.
    o The exceptions are cells that must divide as part of their function, such as lymphocytes.
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
    o Having higher telomerase activity would give cells longer telomeres, allowing them to continue to divide.
    o So you can rule out the answer “decreased telomere length”.
    o This is likely to increase, not decrease, capacity for tissue repair, so you can rule out that answer.
    o This is likely to decrease aging, so you can rule out that answer.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?     o The remaining answer is “increased vulnerability to cancer”. Does this make sense?
    o Cancer cells divide multiple times. Repeated division gradually shortens and loses the telomeres and degrades the DNA ends.
    o But with telomerase present, telomeres can be continually reformed.
    o This removes one of the hurdles for cancer cells to proliferate.
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
    o This question required you to weigh and judge evidence – to Evaluate – and choose the best of the possible answers.
    o Did you remember that telomerase adds telomeres to the ends of DNA?
    o Did you recognize that cancer cells need to divide multiple times?