Reading Comprehension

Lysosomal storage diseases form a category of genetic disorders resulting from defective enzymes that normally function to degrade unneeded molecules in cells. These enzymes do their work in the lysosome, a small compartment in a cell analogous to a garbage disposal. The lysosome contains between thirty and forty different degradative enzymes. When any one of the lysosomal enzymes is defective, the molecules requiring that specific enzyme for their degradation will accumulate and cause that individual's lysosomes to swell enormously. The physiological effects of such swelling on the individual include motor and mental deterioration, often to the point of premature death. But each disease resulting from one specific defective lysosomal enzyme has its own characteristic pathology. The age of onset, rate of progression, and severity of the clinical symptoms observed in patients with the same defective lysosomal enzyme are highly variable. For many years, this variability in patients with the same defective enzyme puzzled scientists. Only recently have researchers begun to answer the riddle, thanks to a genetic analysis of a lysosomal storage disorder known as Tay-Sachs disease.
As in most lysosomal storage diseases, patients suffering from Tay-Sachs disease show both mental and motor deterioration and variability in age of onset, progression, and severity. Physicians have categorized the patients into three groups: infantile, juvenile, and adult, based on onset of the disease. The infantile group begins to show neurodegeneration as early as six months of age. The disease advances rapidly and children rarely live beyond 3 years old. The first symptoms of the disease appear in juvenile cases between 2 and 5 years of age, with death usually occurring around age 15. Those with the adult form generally live out a normal lifespan, suffering from milder symptoms than do those with the infantile and juvenile forms. Researchers hoped that the categorization would yield insight into the cause of the variability of symptoms among Tay-Sachs patients, but this turned out not to be the case.
In Tay-Sachs disease, undegraded materials accumulate mainly in the lysosomes in the brains of patients, but the kinds of molecules left undegraded and the specific identity of the defective lysosomal enzyme responsible for the malfunction were not discovered until the 1950s and 60s, respectively. The main storage molecule was found to be a lipid-like material known as GM2 ganglioside. The defective enzyme was later identified as hexosaminidase. In 1985, the gene coding for the normal hexosaminidase enzyme was cloned and its DNA sequence determined. Shortly thereafter, the DNA sequences of genes encoding hexosaminidase from many Tay-Sachs patients were studied. It soon became apparent that not one or two but many different types of mutations in the hexosaminidase gene could result in Tay-Sachs disease. Some of the mutations prevented the synthesis of any hexosaminidase, preventing all such enzyme activity in the cell. Patients with this type of mutation all had the infantile form of Tay-Sachs disease. Other mutations were found in certain regions of the gene coding for areas of the enzyme known to be critical for its catalytic activity. Such mutations would allow for only extremely crippled hexosaminidase activity. Most of the patients with these mutations clustered in the juvenile category. Adult Tay-Sachs patients presented mutations in the regions of the hexosaminidase gene that were less important for the enzyme's activity than were those affected in juvenile patients. Scientists quickly hypothesized that the variation in age of onset and severity of Tay-Sachs disease correlated with the amount of residual enzymatic activity allowed by the genetic mutation. Though more research is needed to demonstrate similarity with other lysosomal storage diseases, the work done on Tay-Sachs disease has already offered a promising glimpse into the underlying mechanisms of these disorders.

It can be inferred from the passage that which of the following statements is true of lysosomal storage diseases?

They are generally caused by mutations to the hexosaminidase gene.

They are undetectable until physical symptoms are present.

They can be fatal even when allowing some enzymatic activity.

They are most lethal when onset is in a patient's infancy.

Their causes were unknown before the 1950s.

how should we attack this type of questions? frankly speaking, reading this passage itself seems to be sufficient to ensure a disaster in the GMAT. How can we beat the time pressure and the horrible details? Please give some insight.

Uri,
Agreed, i got it in one of the manhattan tests as last rc, it was of 96 lines, iin last 12 minute I coudnt got even a single credited one..huh...manahattanians can be asked what is the best way to deal with this.

ATLEAST POST ALL THE QUESTIONS SO THAT THE QUESTIONS CAN BE DISCUSSED

any chance of getting the OA ?

my answer would be (A)

a terrible thing

I can sumarize tha passage. first paragraph said about deaseas, the second about specific deaseas.

the question is clueless one,which have no hearword or line referent. in this question, we scan 5 choices to see which choice is most likey to be correct, than return to the passage to confirm this choice

however, I can not find the lines which yield the answer.

With a heavily scientific passage like this one, you want to understand how the ideas relate to one another, but you don't necessarily have to understand all of the individual ideas. In other words, you need to have a sense of what they're talking about and how things interrelate, but you don't have to understand *every* specific detail. On this kind, I recommend reading the first few sentences carefully and slowing down to create a mental picture of what they're describing, but skipping over things that are *too* specific -- e.g. you don't have to remember that there are 30-to-40 whatever (I've already forgotten what the third sentence was talking about). Then read enough of the remaining sentences to get a more general sense of what the scientists found or what they're arguing. I personally often read only about half of a particular sentence -- jumping to the next sentence if I feel I got enough of the general idea and they're about to give me a specific detail that I don't need to understand yet (if it says "for example" or it's clear they're about to explain in more detail something that they just said in general terms).

The goal is to build up a mental picture of what they're talking about, not to get ready to pass a science test. Here, they're saying that genetic defects cause a problem in the enzymes that break down different molecules; if the enzymes are defective or aren't working, the molecules build up until huge problems result. Then there are some more specifics about how this plays out in different versions of Tay-Sachs disease. Worse enzyme problems correlate with earlier and worse versions of the disease. That's a very rough summary -- in a biology class, it would be considered pathetic, but we're not prepping for a biology test; this is the GMAT, and it's important to keep the distinction in mind. This kind of crude summary would probably be enough to enable a person to go back and find the specific details needed to answer the actual questions.

Then when you get to the questions, look back to find the specific details. I did this one even more quickly than usual, trying to get a sense of how (if!) it could be handled under real time pressure, but I think the answer is C (Can be fatal even when allowing some enzymatic activity).

Can you post the rest of the questions?

Thank you very much Karen. Yes indeed C is correct answer. See the explanation below:

(C) CORRECT. This choice states that it can be inferred that lysosomal storage diseases "can be fatal even when allowing some enzymatic activity." This can be inferred from the fact that people suffering from juvenile Tay-Sachs have "extremely crippled hexosaminidase activity" and generally live to only 15 years of age .

Other Questions are:

The passage suggests that which of the following lines of inquiry would be most useful in determining the relevance of the research done on Tay-Sachs disease to lysosomal storage diseases generally?

a.Do patients suffering from other lysosomal storage diseases have the same mortality rate as those suffering from Tay-Sachs?

b. Do other lysosomal storage diseases affect the hexosaminidase gene?

c. How many different mutations are present in the defective genes responsible for other lysosomal storage diseases?

d. Does the onset of other lysosomal storage diseases vary with the location of mutations in DNA sequences?

e. What purpose does GM2 ganglioside serve in the human body?

The author of the passage is primarily concerned with

illuminating the physiological consequences of Tay-Sachs disease

explaining the importance of research on a specific disease to other diseases of that type

arguing for a more detailed examination of lysosomal storage diseases

challenging a traditional view of a class of diseases as incomplete

describing the implications of genetic mutations for mortality rates

what are the OA s for above questions

Stupid GMAT questions written for nerds and people with no sense for real business and the reality of business making.

The passage suggests that which of the following lines of inquiry would be most useful in determining the relevance of the research done on Tay-Sachs disease to lysosomal storage diseases generally?

a.Do patients suffering from other lysosomal storage diseases have the same mortality rate as those suffering from Tay-Sachs?

b. Do other lysosomal storage diseases affect the hexosaminidase gene?

c. How many different mutations are present in the defective genes responsible for other lysosomal storage diseases?

d. Does the onset of other lysosomal storage diseases vary with the location of mutations in DNA sequences?

e. What purpose does GM2 ganglioside serve in the human body?

I would say that it is (D). The question asks which of these lines of research would be most useful to determine the relevance of the Tay-Sachs research to lysosomal diseases in general. The article says that the Tay-Sachs research began to solve a long-standing puzzle of these diseases, and it did it by finding this effect of different locations of mutations. So clearly, the best way to find out whether the Tay-Sachs research really pointed the way to the answer for the other diseases is to find out whether they work the same way. So it's D.

The author of the passage is primarily concerned with

illuminating the physiological consequences of Tay-Sachs disease

explaining the importance of research on a specific disease to other diseases of that type

arguing for a more detailed examination of lysosomal storage diseases

challenging a traditional view of a class of diseases as incomplete

describing the implications of genetic mutations for mortality rates

This is one where none of the answer choices seems exactly right, so we have to go for the least-wrong. And by the way, I find that with these "primary concern" or "primary purpose" questions, it's helpful to think about how and why the various wrong answers are wrong, to get a clearer sense of how to judge which one is right. So let's take them one by one:

It's not A because the focus of the article wasn't on a long, detailed description of exactly what happens to the body when people have Tay-Sachs disease.

It could be B because the point was that research on Tay-Sachs may be important for understanding lysosomal storage diseases in general. B seems a little vague, given that the passage actually got more specific about what the scientists have found, but it's not technically untrue.

It's not C because the author didn't talk at length about how inadequate previous research had been and argued that the government needs to provide more funds and scientists need to look more closely and the whole thing needs to be taken more seriously, etc. There was just the one phrase "Though more research is needed to demonstrate similarity with other lysosomal storage diseases..." If C were the right answer, the passage would read more like a persuasive editorial arguing for more funding and research.

It's not D because the passage isn't *challenging* anything -- the author just says scientists were long puzzled and now maybe they've got the answer. If it were challenging a traditional view, it would have sentences like, "This traditional concept is still accepted by many scientists, but new research makes clear that this view is incomplete and should be re-evaluated and modified."

It's not E because E is both too broad and too specific. The passage isn't about any old genetic mutations; it's about the ones that cause lysosomal storage diseases. And the *focus* of the passage wasn't on mortality rates -- the point was the finding about how the location of the mutation determines the severity of the disease.

So it's B.

I was very surprised to find this passage on the Manhattan GMAT practice exam. SOOOOO Boring and hard to understand. Do tough reading passages like this actually pop up on the GMAT?

I took 9.5 minutes to read the passage. How bad is that timing?

I got 2/3 questions right. (got a bit lucky here )

aj5105 wrote:I took 9.5 minutes to read the passage. How bad is that timing?

I got 2/3 questions right. (got a bit lucky here )

at most we have 5 minutes to read and take notes, and 1minute to answer each question or 3,5 minutes to read the passage and a 1,15 min to answer each question