Telomerase

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Telomerase

by tarina » Tue Apr 27, 2010 4:54 am
Telomerase is an enzyme that is produced only in cells that are actively dividing. For this reason it is generally absent from body tissues in adults. Bone marrow is an exception to this rule, however, since even in adults, bone marrow cells continually divide to replace old blood cells. Cancers are another exception, because their cells are rapidly dividing.

The information provided most strongly supports which of the following?

A. Telomerase is the only enzyme that is present in cancerous cells but absent from cells that are not actively dividing.
B. In children, the only body tissues from which telomerase is absent are those in which cells are not rapidly dividing.
C. The presence of telomerase in bone marrow is no indication of bone marrow cancer.
D. Cancer of the bone marrow develops more rapidly than cancer growing in any other kind of adult tissue.
E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue.
Answer: C

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by liferocks » Tue Apr 27, 2010 5:22 am
A. Telomerase is the only enzyme that is present in cancerous cells but absent from cells that are not actively dividing.--cannot conclude it is the only enzyme .eliminated
B. In children, the only body tissues from which telomerase is absent are those in which cells are not rapidly dividing.--premise mentions about adults not children. eliminated
C. The presence of telomerase in bone marrow is no indication of bone marrow cancer.--correct as bone marrow can have Telomerase naturally
D. Cancer of the bone marrow develops more rapidly than cancer growing in any other kind of adult tissue.--no evidence eliminated
E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue. --no evidence eliminated

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by tarina » Tue Apr 27, 2010 7:06 am
liferocks wrote:A. Telomerase is the only enzyme that is present in cancerous cells but absent from cells that are not actively dividing.--cannot conclude it is the only enzyme .eliminated
B. In children, the only body tissues from which telomerase is absent are those in which cells are not rapidly dividing.--premise mentions about adults not children. eliminated
C. The presence of telomerase in bone marrow is no indication of bone marrow cancer.--correct as bone marrow can have Telomerase naturally
D. Cancer of the bone marrow develops more rapidly than cancer growing in any other kind of adult tissue.--no evidence eliminated
E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue. --no evidence eliminated
got that
Thanks!

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by richachampion » Fri Aug 14, 2015 12:54 pm
This is an Inference question that means the inference or conclusion should be guaranteed from the premise.

Telomerase is an enzyme that is produced only in cells that are actively dividing.
For this reason it is generally absent from body tissues in adults.

Hidden Fact: Generally Telomerase is absent from body Tissue in Adults.

Bone marrow is an exception to this rule, however, since even in adults, bone marrow cells continually divide to replace old blood cells.
Cancers are another exception, because their cells are rapidly dividing.

Another Hidden Fact: Bone marrow and Cancers are two exceptions.

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by ddg » Wed Aug 19, 2015 12:14 am
tarina wrote:Telomerase is an enzyme that is produced only in cells that are actively dividing. For this reason it is generally absent from body tissues in adults. Bone marrow is an exception to this rule, however, since even in adults, bone marrow cells continually divide to replace old blood cells. Cancers are another exception, because their cells are rapidly dividing.

The information provided most strongly supports which of the following?

A. Telomerase is the only enzyme that is present in cancerous cells but absent from cells that are not actively dividing.
B. In children, the only body tissues from which telomerase is absent are those in which cells are not rapidly dividing.
C. The presence of telomerase in bone marrow is no indication of bone marrow cancer.
D. Cancer of the bone marrow develops more rapidly than cancer growing in any other kind of adult tissue.
E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue.
Answer: C
Lets eliminate the wrong choices first, shall we? :)

A. Telomerase is the only enzyme that is present in cancerous cells but absent from cells that are not actively dividing. To say 'T' is the ONLY enzyme is - going to an extreme conclusion that there are no other enzymes present. our premises don't state so.


B. In children, the only body tissues from which telomerase is absent are those in which cells are not rapidly dividing. We are not talking about children in general, we are talking about adults. Cancer may be present in children as well, but that is a another topic altogether - not touched by this passage.


C. The presence of telomerase in bone marrow is no indication of bone marrow cancer. Hmm, lets keep this.


D. Cancer of the bone marrow develops more rapidly than cancer growing in any other kind of adult tissue. We are NOT comparing different types of cancer here. out of scope.


E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue. Hmm, keep this in, too.

Comparing C and E:


Again eliminate first!

E) says level of T production in cancerous tissue > T production in NC Tissue
C) Presence of T in the BM isn't indication of BM Cancer.

If in doubt, go back to your framework:
Telomerase is an enzyme that is produced only in cells that are actively dividing. For this reason it is generally absent from body tissues in adults. Bone marrow is an exception to this rule, however, since even in adults, bone marrow cells continually divide to replace old blood cells. Cancers are another exception, because their cells are rapidly dividing.

T is an enzyme produced when cells are ACTIVELY DIVIDING ---> So, T is GENERALLY (not completely) absent from BT in adults ---> BM is an exception because BMC are continually dividing ---> Cancer is another exception as well.

Two examples of exception are shown. They are just stated. Not compared. It is NOT the case:
For C: If cancer has T ---> BM has T ---> BM Cancer is present (Ask yourself this: Is it true? you'll feel that No, I can't link these two with this analogy here)

Rather, Cancer has T (ok, fine) ---> BM has T ---> BM C is not necessarily present (ask yourself again, and you'll see, yea I can say that :))

For E: T is MORE present in C cells > than in NC Cells (Not necessarily true, because T levels may be same, maybe another factor or enzyme is triggering T, this MAY or MAY NOT be true -->Conclusion MUST be true from premises.

So E eliminated.

C is your answer :)

Hope this helps!

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by thuyduong91vnu » Tue Sep 13, 2016 3:05 am
Hi,

Could someone help to explain why choice E is incorrect?

According to the given information, "telomerase" is found only in some cells actively dividing (such as bone marrow, cancers... in adults), so why couldn't we conclude that because it is not found elsewhere, "the level of telomerase production is always higher in cancerous tissue (which has telomerase) than in noncancerous tissue (which does not have telomerase)"?

Thanks for helping!

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by richachampion » Tue Sep 13, 2016 4:57 am
thuyduong91vnu wrote:Hi,

Could someone help to explain why choice E is incorrect?

According to the given information, "telomerase" is found only in some cells actively dividing (such as bone marrow, cancers... in adults), so why couldn't we conclude that because it is not found elsewhere, "the level of telomerase production is always higher in cancerous tissue (which has telomerase) than in noncancerous tissue (which does not have telomerase)"?

Thanks for helping!

Telomerase is an enzyme that is produced only in cells that are actively dividing. For this reason it is generally absent from body tissues in adults.
Bone marrow is an exception to this rule, however, since even in adults, bone marrow cells continually divide to replace old blood cells. Cancers are another exception, because their cells are rapidly dividing.

We can interpret the above argument in this way =
Even when Bone marrow and cancer cells actively dividing the Telomerase is still not present in them. or Its inverse is also true that the presence of Telomerase in bone marrow is no indication of the bone marrow cancer.

This is the reason why C is correct.


E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue.

Since the "level of telomerase production" is compared in cancerous and non canerous tissues.
This OPTION means that telomerase is present both in cancerous and non cancerous tissue and this interpretation is not correct.

This make this option Out of Scope. In one way it is also challenging the premise and thus can be eliminated.
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by thuyduong91vnu » Wed Sep 14, 2016 6:54 am
Hi richachampion,

Thank for your explanation, but I still find it somewhat difficult to understand why E is out of scope and also challenges the premise :(

The given information is:
Telomerase is only in cells that are actively dividing, including Bone marrow cells and Cancer cells
=> So we expect that Telomerase presents in cancerous tissues, and NOT in noncancerous tissues, right?
=> So why couldn't we conclude that the level of Telomerase production in cancerous tissues (which has such production) is higher than that in noncancerous tissues (which does not have such production)?

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by [email protected] » Wed Sep 14, 2016 7:42 am
thuyduong91vnu wrote: => So we expect that Telomerase presents in cancerous tissues, and NOT in noncancerous tissues, right?
=> So why couldn't we conclude that the level of Telomerase production in cancerous tissues (which has such production) is higher than that in noncancerous tissues (which does not have such production)?
We know from the prompt that noncancerous bone marrow does produce Telomerase. Imagine that you're comparing cancerous tissue to noncancerous bone marrow tissue. We know that telomerase production is occurring in both. Is there anything from the prompt to suggest that the production level is higher in the cancerous tissue? So while most noncancerous tissue does not produce telomerase, the production occurring in the bone marrow prevents us from accepting the claim in E that production is always higher in cancerous tissue. (Note those extreme modifiers, such as "always.")
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by thuyduong91vnu » Wed Sep 14, 2016 6:20 pm
Thanks for your help, David! It is very clear to me now :D

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by MBA Challengers » Fri Sep 16, 2016 2:20 am
tarina wrote:Telomerase is an enzyme that is produced only in cells that are actively dividing. For this reason it is generally absent from body tissues in adults. Bone marrow is an exception to this rule, however, since even in adults, bone marrow cells continually divide to replace old blood cells. Cancers are another exception, because their cells are rapidly dividing.

The information provided most strongly supports which of the following?

A. Telomerase is the only enzyme that is present in cancerous cells but absent from cells that are not actively dividing.
B. In children, the only body tissues from which telomerase is absent are those in which cells are not rapidly dividing.
C. The presence of telomerase in bone marrow is no indication of bone marrow cancer.
D. Cancer of the bone marrow develops more rapidly than cancer growing in any other kind of adult tissue.
E. The level of telomerase production is always higher in cancerous tissue than in noncancerous tissue.
Answer: C
Let's take the noting down premises approach to the question:
1. T enzyme is present in rapidly dividing cells
2. T is absent from adult bodies except 2 cases
3. Case 1: Bone marrow as cells rapidly divide to replace old blood
4. Case 2: In the occurence of cancer in the body as that also leads to rapid division of cells

Now start looking at answer options to see what makes sense as a direct inference:
A. The passage does not detail out whether there are any other enzymes in cancerous cells. INCORRECT
B. While the passage tells us about where the enzyme occurs in adult bodies, it tells us nothing about body parts in children where it might be present or absent. INCORRECT
C. The passage clearly mentions 2 instances where the enzyme would be found. Thus, bone marrow cells divide without occurence of cancer also and have the enzyme with or without Cancer. The enzyme's presence in the bone marrow is not evidence of cancer. CORRECT
D. While bone marrow and cancer both have been stated to lead to rapid division of cells, there is no implication of that being a factor in the pace of the spreading of the disease. INCORRECT
E. This is a tricky option because while the cancerous tissue will have the enzyme, this option eliminates the possibility of the a comparison between bone marrow tissue and a cancerous tissue. Also, the passage does not give any relative numbers of the enzyme in the two types of tissues. INCORRECT

So, the answer in this case is clearly C.
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