Reading Comprehension

Hi All,

In the below question, [spoiler]OA = D[/spoiler]....can someone please tell why not B ?

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Symptoms of Parkinson’s Disease, such as tremors, are thought to be caused by low dopamine levels in the brain. Current treatments of Parkinson’s disease are primarily reactionary, aiming to replenish dopamine levels after dopamine-producing neurons in the brain have died. Without a more detailed understanding of the behavior of dopamine-producing neurons, it has been impossible to develop treatments that would prevent the destruction of these neurons in Parkinson’s patients.

Recent research provides insight into the inner workings of dopamine-producing neurons, and may lead to a new drug treatment that would proactively protect the neurons from decay. By examining the alpha-synuclein protein in yeast cells, scientists have determined that toxic levels of the protein have a detrimental effect on protein transfer within the cell. More specifically, high levels of alpha-synuclein disrupt the flow of proteins from the endoplasmic reticulum, the site of protein production in the cell, to the Golgi apparatus, the component of the cell that modifies and sorts the proteins before sending them to their final destinations within the cell. When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies.

With this in mind, researchers conducted a genetic screen in yeast cells in order to identify any gene that works to reverse the toxic levels of alpha-synuclein in the cell. Researchers discovered that such a gene does in fact exist, and have located the genetic counterpart in mammalian nerve cells, or neurons. This discovery has led to new hopes that drug therapy could potentially activate this gene, thereby suppressing the toxicity of alpha-synuclein in dopamine-producing neurons.

While drug therapy to suppress alpha-synuclein has been examined in yeast, fruitflies, roundworms, and cultures of rat neurons, researchers are hesitant to conclude that such therapies will prove successful on human patients. Alpha-synuclein toxicity seems to be one cause for the death of dopamine-producing neurons in Parkinson’s patients, but other causes may exist. Most scientists involved with Parkinson’s research do agree, however, that such promising early results provide a basis for further testing.

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It can be inferred from the passage that a yeast cell with toxic levels of alpha-synuclein will die because

a) low levels of dopamine will disrupt the flow of proteins from the endoplasmic reticulum to the Golgi aparatus
b) the gene that suppresses alpha-synuclein is missing or is not functioning properly in such yeast cells
c) drug therapy has proven to be ineffective in yeast cells
d) the normal distribution of proteins to the different cell components outside the Golgi apparatus will be affected
e) alpha-synuclein is by nature a toxic protein

goelmohit2002 wrote:Hi All,

In the below question, [spoiler]OA = D[/spoiler]....can someone please tell why not B ?

=============================================
Symptoms of Parkinson’s Disease, such as tremors, are thought to be caused by low dopamine levels in the brain. Current treatments of Parkinson’s disease are primarily reactionary, aiming to replenish dopamine levels after dopamine-producing neurons in the brain have died. Without a more detailed understanding of the behavior of dopamine-producing neurons, it has been impossible to develop treatments that would prevent the destruction of these neurons in Parkinson’s patients.

Recent research provides insight into the inner workings of dopamine-producing neurons, and may lead to a new drug treatment that would proactively protect the neurons from decay. By examining the alpha-synuclein protein in yeast cells, scientists have determined that toxic levels of the protein have a detrimental effect on protein transfer within the cell. More specifically, high levels of alpha-synuclein disrupt the flow of proteins from the endoplasmic reticulum, the site of protein production in the cell, to the Golgi apparatus, the component of the cell that modifies and sorts the proteins before sending them to their final destinations within the cell. When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies.

With this in mind, researchers conducted a genetic screen in yeast cells in order to identify any gene that works to reverse the toxic levels of alpha-synuclein in the cell. Researchers discovered that such a gene does in fact exist, and have located the genetic counterpart in mammalian nerve cells, or neurons. This discovery has led to new hopes that drug therapy could potentially activate this gene, thereby suppressing the toxicity of alpha-synuclein in dopamine-producing neurons.

While drug therapy to suppress alpha-synuclein has been examined in yeast, fruitflies, roundworms, and cultures of rat neurons, researchers are hesitant to conclude that such therapies will prove successful on human patients. Alpha-synuclein toxicity seems to be one cause for the D€@th of dopamine-producing neurons in Parkinson’s patients, but other causes may exist. Most scientists involved with Parkinson’s research do agree, however, that such promising early results provide a basis for further testing.

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It can be inferred from the passage that a yeast cell with toxic levels of alpha-synuclein will die because

a) low levels of dopamine will disrupt the flow of proteins from the endoplasmic reticulum to the Golgi aparatus
b) the gene that suppresses alpha-synuclein is missing or is not functioning properly in such yeast cells
c) drug therapy has proven to be ineffective in yeast cells
d) the normal distribution of proteins to the different cell components outside the Golgi apparatus will be affected
e) alpha-synuclein is by nature a toxic protein

i think B can be eliminated on the basis of boldface statements in para 3 above..which says that the gene is present but need activation to supress toxicity.. Choice B says that the gene is missing..
IMO D is not very convincing as well. check the boldface statements in para 2..i am not sure whether D could be the reason for the problem mentioned in question asked..Among all the choices D seems the best..

Thanks.

But IMO D is talking what happens after this......i.e. "effect"

and B is talking about "cause"....i.e. what causes flow to stop.....

Also last line of 2nd para says that "When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies."

So why are we preferring to pick the answer as effect....i.e. D and not cause i.e. B.....which IMO what last line of 2nd para says....

Please tell what I am missing here ?

goelmohit2002 wrote:Thanks.

But IMO D is talking what happens after this......i.e. "effect"

and B is talking about "cause"....i.e. what causes flow to stop.....

Also last line of 2nd para says that "When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies."

So why are we preferring to pick the answer as effect....i.e. D and not cause i.e. B.....which IMO what last line of 2nd para says....

Please tell what I am missing here ?

B is not the cause..Cause is that the gene is inactivated but B says that gene is missing.. Passage clearly says that gene is already present.
i also feel that D is not directly inferred in the passage and hence not the best answer for this question but i think that acc. to other answer choices D is the best among all the answer choices..

ketkoag wrote:

goelmohit2002 wrote:Thanks.

But IMO D is talking what happens after this......i.e. "effect"

and B is talking about "cause"....i.e. what causes flow to stop.....

Also last line of 2nd para says that "When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies."

So why are we preferring to pick the answer as effect....i.e. D and not cause i.e. B.....which IMO what last line of 2nd para says....

Please tell what I am missing here ?

B is not the cause..Cause is that the gene is inactivated but B says that gene is missing.. Passage clearly says that gene is already present.
i also feel that D is not directly inferred in the passage and hence not the best answer for this question but i think that acc. to other answer choices D is the best among all the answer choices..

Hi Ketkoag,

B also says that Gene is not working properly....isn't inactivation more or less means not activated.....

Looks like there is some subtility that I am missing here. Can you please help clarify.

goelmohit2002 wrote:

ketkoag wrote:

goelmohit2002 wrote:Thanks.

But IMO D is talking what happens after this......i.e. "effect"

and B is talking about "cause"....i.e. what causes flow to stop.....

Also last line of 2nd para says that "When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies."

So why are we preferring to pick the answer as effect....i.e. D and not cause i.e. B.....which IMO what last line of 2nd para says....

Please tell what I am missing here ?

B is not the cause..Cause is that the gene is inactivated but B says that gene is missing.. Passage clearly says that gene is already present.
i also feel that D is not directly inferred in the passage and hence not the best answer for this question but i think that acc. to other answer choices D is the best among all the answer choices..

Hi Ketkoag,

B also says that Gene is not working properly....isn't inactivation more or less means not activated.....

Looks like there is some subtility that I am missing here. Can you please help clarify.

there is a very thin line between not working properly and inactivation..
not working properly means that the gene is activated but not working properly.. inactivation means that gene cannot work at all, properly or improperly.. and that is why "missing" is introduced in the sentence to make the point more clear..

high levels of alpha-synuclein=> interruption of smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus=>cell death

Q asks for the cause.
best brought out by D. cell dies because smooth transfer is affected

B. doesnt cut it as the gene supressing alpha-synuclein though present in yeast cells has to be activated by a drug therapy to counter the to toxicity of alpha-synuclein.
the gene as is cannot/does not counter the toxicity. scientists are hoping drug therapy would counter the toxicity of alpha-synuclein in future.
( this thing is mentioned in the context of finding a cure for toxicity/cell death, not in the context of finding the cause of cell death)

Stacey Koprince wrote:Received a PM asking me to respond.

PD symptoms caused by low DPMN.
Now: replace DPMN after DPMN neurons die
How to prevent neurons from dying?

New research might help.
AS protein in yeast: toxic levels affect protein movement
<some detail about what specifically is hindered>
when movement isn't correct, cell dies

(me thinking: okay, that was about something going on in yeast cells, not something in humans. but maybe human cells work the same way?)

yeast: any genes that reduce levels of AS protein?
yes, and it's not just in yeast; humans have this too!
could we activate the gene to reduce levels in humans?

Maybe. Studied in other things, but not humans. Maybe other things besides AS protein are going wrong. But research is promising.

Question:
why will yeast cell with toxic AS levels die? (inference)

relevant text from passage (from my notes):
AS protein in yeast: toxic levels affect protein movement
and
when movement isn't correct, cell dies

(A) not low levels
(B) at the point this was discussed, they didn't even know such a gene might exist. We also don't know how that gene is supposed to function properly, so we don't know whether this is the cause of toxic levels. Also, the question is asking not why they'll have toxic levels, but why toxic levels will cause the cells to die.
(C) nothing about drug therapy in yeast
(D) hmm. I skipped the Golgi stuff. Let's read it: toxic AS levels --> disrupting movement of proteins from ER to Golgi --> cells die. So, yep, the fact that the normal distribution is disrupted in some way leads the cells to die.
(E) no evidence for this in passage

Stacey U said there is no evidence for option E . In the second para the line explicitly mentions " By examining the alpha-synuclein protein in yeast cells, scientists have determined that toxic levels of the protein have a detrimental effect on protein transfer within the cell." Please explain .

@ Mundasingh - Stacy stated that E is unsupported. Here is my basis for this.

IMO Choice E, which states that the alpha-synuclein is by nature a toxic protein, is not supported as the passages states that toxic levels or high levels ( but not any levels as suggested by the answer choice E) of of alpha-synuclei disrupt the smooth transfer of proteins and ultimately causes the death of cells.

@ Stacy , whats the ballpark time spent on such a question , including reading , mapping and answering this question. Thanks for the details. [/i]

Haaress wrote:@ Mundasingh - Stacy stated that E is unsupported. Here is my basis for this.

IMO Choice E, which states that the alpha-synuclein is by nature a toxic protein, is not supported as the passages states that toxic levels or high levels ( but not any levels as suggested by the answer choice E) of of alpha-synuclei disrupt the smooth transfer of proteins and ultimately causes the death of cells.

@ Stacy , whats the ballpark time spent on such a question , including reading , mapping and answering this question. Thanks for the details. [/i]

I have pmed stacy regarding this.I hope she replies to my query

goelmohit2002 wrote: More specifically, high levels of alpha-synuclein disrupt the flow of proteins from the endoplasmic reticulum, the site of protein production in the cell, to the Golgi apparatus, the component of the cell that modifies and sorts the proteins before sending them to their final destinations within the cell. When the smooth transfer of proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies.

(D) the normal distribution of proteins to the different cell components outside the Golgi apparatus will be affected

We can see from the above line in the paragraph that the cell's life depends on the smooth transfer of proteins to the cell. Hence D is the cause as well as the correct answer.

Please note the bold key words in my explanation. Hope it helps.

Q: It can be inferred from the passage that a yeast cell with toxic levels of alpha-synuclein will die because

We need to look for the ultimate reason: root cause right?

Ref. The excerpt from passage and bold key words:

By examining the alpha-synuclein protein in yeast cells, scientists have determined that toxic levels of the protein have a detrimental effect on protein transfer within the cell. ......................................
........................ Golgi apparatus, the component of the cell that modifies and sorts the proteins before sending them to their final destinations within the cell.

Explanation:

Among various components of cell, Endoplasmic reticulum is responsible for the production of Protein within the cell which acts a source for Golgi Apparatus, another component within the cell , which subsequently modifies and sorts the protein, thereby acts as a modifier/distributor within the cell and sends/transfers outside to various final destinations within the cell.

Now if we analyze the supply chain of protein within the cell, the key areas where its supply/transfer can be affected are the production unit i.e. Endoplasmic reticulum or the distribution/transfer unit: the Golgi Apparatus.

Also, it is explicitly mentioned that alpha-synuclein protein affects the transfer of protein within the cell i.e. it affects the distribution/transfer unit i.e. Golgi...hence the distribution/supply of protein outside the Golgi stops and cell dies. So the root cause is disruption in distribution/transfer.

Now, option D says:

d) the normal distribution of proteins to the different cell components outside the Golgi apparatus will be affected

If you note the bold key words in the option and co-relate to the explanation above, you would feel that it obviously falls into the line. Hence IMO: D.

It can be inferred from the passage that a yeast cell with toxic levels of alpha-synuclein will die because

a) low levels of dopamine will disrupt the flow of proteins from the endoplasmic reticulum to the Golgi aparatus [reverse: dopamine is becoming low due to reduction of protien flow]
b) the gene that suppresses alpha-synuclein is missing or is not functioning properly in such yeast cells [ toxic is suppessing alpha--blah blah]
c) drug therapy has proven to be ineffective in yeast cells [last para : it is successful]
d) the normal distribution of proteins to the different cell components outside the Golgi apparatus will be affected [transfer process mishap can cause cell death para 2]
e) alpha-synuclein is by nature a toxic protein [ 2nd para: No it is not : toxic is corrupting it]

Here is MYGO:
topic : symptions of parkison disease
scope: aiming to generate more dopamine by more nuerons/need resarch


2nd para: POV : reason for cell death/new R&D
new research helps neruon decay
we know how cell dies..transfer process mishap

3rd para:
Solution found : a gene reverses toxic levels
this will reduce toxics

4th: POV is -ve
On humans this will not work
toxics are not the only cause for nueron death..scientist agreed
the above test on non humans is giving hope

Only D. Not sure where the passage even talks about some gene not functioning properly. B is out of question. In fact I felt that the answers were pretty straight forward.