Reading Comprehension

PT117 · S1 · P3 · Q20 NGF

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The survival of nerve cells, as well as their performance of some specialized functions, is regulated by chemicals known as neurotrophic factors, which are produced in the bodies of animals, including humans.

Topic

The discovery and role of nerve growth factor (NGF) and neurotrophic factors in nerve cell survival and development.

Framework

Highlight Noteworthy (with a touch of Answer / Explain—explaining how NGF works and why it's important)

Main Point

Rita Levi-Montalcini’s discovery of nerve growth factor (NGF) was a landmark achievement that explained how nerve cells survive, develop, and connect, revealing the key role of neurotrophic factors in animal biology. (The Most Valuable Sentence: The first paragraph’s closing sentence: )

P1: Introduction to Neurotrophic Factors and Levi-Montalcini’s Discovery

We’re introduced to neurotrophic factors—special chemicals that help nerve cells survive and work. Rita Levi-Montalcini discovered the first important one (NGF), which forever changed how scientists thought about nerve cells and earned her a Nobel Prize.

P2: The Experiments and Discovery of NGF

Levi-Montalcini thought lots of nerve cells were meant to die off during development, and she found evidence for this in embryos. Noticing that mouse tumors caused unusual nerve growth in chick embryos, she guessed a chemical from the tumors was responsible. By using tissue cultures, she proved that a specific protein produced by the tumors—NGF—was making this happen.

P3: The Function and Importance of NGF

NGF turned out to be the first of many such growth factors in animals. Thanks to Levi-Montalcini’s work and later research, scientists now know NGF helps nerve cells not just grow, but also survive and connect to the right targets during development. If nerve cells don’t get NGF, they can’t survive, which makes this protein crucial for healthy nervous systems, especially outside the brain and spinal cord.

20.

Which one of the following is most strongly supported by the information in the passage?

Some of the effects that
Out of Scope: other than NGF
The passage tells us that other neurotrophic factors have been discovered, other than NGF. But NGF was the factor discovered by Levi-Montalcini in her chick experiment. The final sentence of the 2nd paragraph says: Further research identified a specific substance contributed by the mouse tumors that was responsible for the effects: NGF.
5% picked this
Although NGF was the first
Unknown Comparison: more thoroughly
We know that other neurotrophic factors have been discovered, but there isn't any text that makes a comparison about any of them being more thoroughly understood than is NGF. The final paragraph tells us a lot about NGF, too, so it seems like NGF is pretty well understood.
21% picked this
In her research in the
Out of Scope: other factors
We only ever hear about Levi-Montalcini discovering NGF. The first sentence of the final paragraph says that NGF was the first of many cell-growth factors to be found, but it doesn't say or suggest that Levi-Montalcini found any of these other factors. The following sentence returns to talking about Levi-Montalcini because the rest of the final paragraph tells us all that we now know about NGF, some of which we learned from Levi-Montalcini's research in the 40s / 50s.
4% picked this
Correct
Some neurotrophic factors other than
Why this is right
This is as obnoxious as Inference + Undefined Target can get. They're just asking us to find a needle-in-a-haystack. And sometimes that needle is found early on, in one of the "throwaway" details we might read in the 1st paragraph. The very first sentence says that the survival of nerve cells is regulated by chemicals known as neurotrophic factors. It also says that nerve cells' performance of some specialized functions is regulated by chemicals known as neurotrophic factors. We only hear about NGF in the passage, and it regulates the survival of nerve cells. So presumably these other neurotrophic factors are involved in regulating the performance of some specialized functions of nerve cells. But those functions are not specifically identified by the passage.
Skill tested: Inference · how this choice captures the passage's function is the move to repeat next time.
63% picked this
The effects of NGF that
Out of Scope: also caused
We don't have any evidence that the other neurotrophic factors also have the effect of controlling the survival of nerve cells. The first sentence says that "survival of cells as well as performance of specialized functions is regulated by neurotrophic factors". That doesn't mean that all neurotrophic factors do both things. We can say "color of eyes as well as height are regulated by genes". That doesn't mean that every type of gene regulates eye color and height. That sentence can just mean that some genes handle eye color, other handle height.
7% picked this

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