NGF

Answer choices

1. A

   Out of Scope: other than NGF5% picked this

   Some of the effects that the author describes as occurring in Levi-Montalcini’s culture of chick embryo extract were due to

   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%
2. B

   Unknown Comparison: more thoroughly22% picked this

   Although NGF was the first neurotrophic factor to be identified, some other such factors are

   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.

   22%
3. C

   Out of Scope: other factors4% picked this

   In her research in the 1940s and 1950s, Levi-Montalcini identified other neurotrophic factors in

   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%
4. D

   Correct62% picked this

   Some neurotrophic factors other than NGF perform functions that are not specifically identified

   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.

   62%
5. E

   Out of Scope: also caused7% picked this

   The effects of NGF that Levi-Montalcini noted in her chick embryo experiment are also caused by other neurotrophic factors

   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%