Erythrovirus412

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romitrock: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Tue Dec 15, 2015 12:35 am

by romitrock » Sat Mar 05, 2016 11:40 am

The Erythrovirus412, which affects farmed Atlantic salmon, infects human beings by adhering to red blood cells. The virus elevates the body's white blood cell count, indicating that the body is fighting an infection. Surprisingly, when a group of recently-infected people were tested, the proportion of white blood cells compared to red blood cells in their bodies was similar to that of an uninfected person.
Which of the following, if true, most helps to explain the surprising finding?

A.An infected body can sometimes attempt to stimulate its immune system by producing an unusually high number of white blood cells
B.Ingestion of infected salmon by people whose immune system is already weak can destroy a significant proportion of red blood cells in the body
C.The Nucleic Acid Test (NAT) used to detect the virus has revealed that the virus embeds itself in the plasma constituting the lining of a cell in addition to circulating through blood cells.
D.The virus multiplies by increasing the number of its host cells
E.Most people infected by the virus develop fever two weeks after being infected, but show no other symptoms of the disease

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Source: Beat The GMAT — Critical Reasoning | Sat Mar 05, 2016 11:40 am

romitrock: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Tue Dec 15, 2015 12:35 am

by romitrock » Sat Mar 05, 2016 11:41 am

@GMATGuruNY : PLS Help

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usefulcreature: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Tue Feb 02, 2016 1:05 am

by usefulcreature » Sat Mar 05, 2016 11:16 pm

D. The virus multiplies by increasing the number of its host cells

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romitrock: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Tue Dec 15, 2015 12:35 am

by romitrock » Mon Mar 07, 2016 2:00 am

yes the answer is D. But what is the reasoning??

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ceilidh.erickson: GMAT Instructor; Posts: 2095; Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members; Thanked: 1443 times

by ceilidh.erickson » Mon Mar 07, 2016 8:08 am

The Erythrovirus412, which affects farmed Atlantic salmon, infects human beings by adhering to red blood cells. The virus elevates the body's white blood cell count, indicating that the body is fighting an infection. Surprisingly, when a group of recently-infected people were tested, the proportion of white blood cells compared to red blood cells in their bodies was similar to that of an uninfected person.

Which of the following, if true, most helps to explain the surprising finding?

A. An infected body can sometimes attempt to stimulate its immune system by producing an unusually high number of white blood cells
B. Ingestion of infected salmon by people whose immune system is already weak can destroy a significant proportion of red blood cells in the body
C. The Nucleic Acid Test (NAT) used to detect the virus has revealed that the virus embeds itself in the plasma constituting the lining of a cell in addition to circulating through blood cells.
D. The virus multiplies by increasing the number of its host cells
E. Most people infected by the virus develop fever two weeks after being infected, but show no other symptoms of the disease

If we're asked to EXPLAIN a surprising finding / discrepancy / paradox, first we have to discover why the finding is surprising --> we have to infer what the EXPECTED result would have been.

Given: The virus elevates the body's white blood cell count --> infected people have more white blood cells

You would expect: Infected people have a higher proportional white blood cell count than uninfected people do.

Surprising Result: the proportion of white blood cells compared to red blood cells in their bodies was similar to that of an uninfected person

How to explain: We know that white blood cell counts are going up. If the proportion stays the same, though, that must mean that the red blood cell count is also going up.

A. An infected body can sometimes attempt to stimulate its immune system by producing an unusually high number of white blood cells
This does the opposite of what we're looking for - it would support the idea that there was a HIGHER proportion of white blood cells, not the same.

B. Ingestion of infected salmon by people whose immune system is already weak can destroy a significant proportion of red blood cells in the body
Same as above - this would indicate red blood cell levels going DOWN, not up.

C. The Nucleic Acid Test (NAT) used to detect the virus has revealed that the virus embeds itself in the plasma constituting the lining of a cell in addition to circulating through blood cells.
Irrelevant to the proportion of white:red blood cells.

D. The virus multiplies by increasing the number of its host cells
This would indicate red blood cells going up - correct!

E. Most people infected by the virus develop fever two weeks after being infected, but show no other symptoms of the disease
Symptoms are irrelevant to the proportion question.

Answer D is the only one that addresses an increasing number of red blood cells - the virus' host cells.

Last edited by ceilidh.erickson on Mon Mar 07, 2016 8:17 am, edited 1 time in total.

Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education

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ceilidh.erickson: GMAT Instructor; Posts: 2095; Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members; Thanked: 1443 times

by ceilidh.erickson » Mon Mar 07, 2016 8:14 am

For more on how to approach these EXPLAIN A DISCREPANCY question types, see here:

https://www.beatthegmat.com/resolve-the- ... tml#717366

https://www.beatthegmat.com/critical-rea ... tml#725224

https://www.beatthegmat.com/when-there-i ... tml#716501

https://www.beatthegmat.com/centralia-s- ... tml#544276

https://www.beatthegmat.com/cr-t155437.html#548469

Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education

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romitrock: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Tue Dec 15, 2015 12:35 am

by romitrock » Thu Mar 10, 2016 1:43 am

thanks ceilidh.erickson for posting more questions of this type.

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peter456: Junior | Next Rank: 30 Posts; Posts: 24; Joined: Sun Sep 20, 2015 12:47 am

by peter456 » Tue Mar 22, 2016 3:38 pm

ceilidh.erickson wrote:
The Erythrovirus412, which affects farmed Atlantic salmon, infects human beings by adhering to red blood cells. The virus elevates the body's white blood cell count, indicating that the body is fighting an infection. Surprisingly, when a group of recently-infected people were tested, the proportion of white blood cells compared to red blood cells in their bodies was similar to that of an uninfected person.

Which of the following, if true, most helps to explain the surprising finding?

A. An infected body can sometimes attempt to stimulate its immune system by producing an unusually high number of white blood cells
B. Ingestion of infected salmon by people whose immune system is already weak can destroy a significant proportion of red blood cells in the body
C. The Nucleic Acid Test (NAT) used to detect the virus has revealed that the virus embeds itself in the plasma constituting the lining of a cell in addition to circulating through blood cells.
D. The virus multiplies by increasing the number of its host cells
E. Most people infected by the virus develop fever two weeks after being infected, but show no other symptoms of the disease
If we're asked to EXPLAIN a surprising finding / discrepancy / paradox, first we have to discover why the finding is surprising --> we have to infer what the EXPECTED result would have been.

Given: The virus elevates the body's white blood cell count --> infected people have more white blood cells

You would expect: Infected people have a higher proportional white blood cell count than uninfected people do.

Surprising Result: the proportion of white blood cells compared to red blood cells in their bodies was similar to that of an uninfected person

How to explain: We know that white blood cell counts are going up. If the proportion stays the same, though, that must mean that the red blood cell count is also going up.

D. The virus multiplies by increasing the number of its host cells
This would indicate red blood cells going up - correct!

Answer D is the only one that addresses an increasing number of red blood cells - the virus' host cells.

Hi Erikson,

D suggests that by increasing the No of host's cells, the red blood cells outnumber the white blood cells. I get confused here.

An increase in the host's cells might refer to the white blood cells, the red blood cells, or both.

Pls help clarify how "host's cells" refers to "red blood" cells.

Thanks

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MartyMurray: Legendary Member; Posts: 2135; Joined: Mon Feb 03, 2014 9:26 amFollowed by: 140 members; Location: https://martymurraycoaching.com/; Thanked: 955 times; GMAT Score:800

by MartyMurray » Tue Mar 22, 2016 4:25 pm

peter456 wrote:Hi Erikson,

D suggests that by increasing the No of host's cells, the red blood cells outnumber the white blood cells. I get confused here.

An increase in the host's cells might refer to the white blood cells, the red blood cells, or both.

Pls help clarify how "host's cells" refers to "red blood" cells.

Thanks

The truth is that you have found a weakness in this question.

While the prompt does state that the Erythrovirus412 infects human beings by adhering to red blood cells, neither the prompt nor answer choice D makes entirely clear that the virus's host cells are the red blood cells of human beings. The red blood cells mentioned in the prompt could be those of the salmon or the red blood cells may be those of human beings and yet somehow not the "host cells" of the virus.

So in order to use answer choice D to explain the finding, you have to assume that given what is said in the prompt "adhering to red blood cells" means that some or all of the "host cells" of the virus are the red blood cells of human beings, and that white blood cells are not "host cells".

That having been said, that assumption is fairly safe, as given any reasonable understanding of the other answer choices, none of the other answer choices explain the finding.

Marty Murray
Perfect Scoring Tutor With Over a Decade of Experience
MartyMurrayCoaching.com
Contact me at [email protected] for a free consultation.

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ceilidh.erickson: GMAT Instructor; Posts: 2095; Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members; Thanked: 1443 times

by ceilidh.erickson » Tue Mar 22, 2016 6:31 pm

peter456 wrote: Hi Erikson,

D suggests that by increasing the No of host's cells, the red blood cells outnumber the white blood cells. I get confused here.

An increase in the host's cells might refer to the white blood cells, the red blood cells, or both.

Pls help clarify how "host's cells" refers to "red blood" cells.

Thanks

I think the misunderstanding is actually this: the answer choice says "host cells," not "host's cells." In medical terminology, a "host cell" is specifically the cell that embodies a particular pathogen. Since we're told that these viruses "infects human beings by adhering to red blood cells," then the red blood cell are the HOST cell. (Think of "host" as just a modifier describing the type of cell).

If the answer choice had been written "host's" (possessive), then you would be right - the human would be the host (presumably), and any human cell could be the host's cell.

This is just a quirk of English usage - not an issue you're likely to run into often. The moral here, if there is one, is to read carefully! Don't make assumptions about what's written.

Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education

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