Symptoms of Parkinson’s Disease, such as tremors, are thought to be

1.
This is a general question asking about the function of the third paragraph. To answer this question, it is helpful to examine the general role that each paragraph in
the passage plays. The first paragraph introduces the problem: researchers have not known enough about neurons to effectively treat the symptoms of Parkinson’s Disease. The second paragraph introduces new research in yeast cells. The third paragraph makes the connection between this research and neurons affected by Parkinson’s disease. In other words, the third paragraph serves to transition from the technical detail of the yeast cell research in paragraph two to the implications of this research on Parkinson’s treatment.
(A) While the third paragraph mentions genetic counterparts in yeast cells and mammalian nerve cells, its role is not to highlight similarities between the cells. In
fact, no additional similarities are mentioned.
(B) The third paragraph does not get into the details of genetic screening methods.
(C) The third paragraph does not explain the roles of various cellular components. The second paragraph does discuss the roles of the endoplasmic reticulum and the
Golgi apparatus, but this discussion is not continued in the third paragraph.
(D) The third paragraph does not actually identify, or name, any genes. Rather, it explains that researchers were able to identify a specific gene in yeast cells and its
counterpart in mammalian nerve cells.
(E) CORRECT. The third paragraph relates the genetic testing in yeast cells to the broader issue of Parkinson’s treatment: “Researchers discovered that such a gene
does in fact exist [in yeast cells], 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.”

2.
This is a specific question that can be answered by examining the information given in the second paragraph.
(A) According the second paragraph, “high levels of alpha-synuclein disrupt the flow of proteins from the endoplasmic reticulum…to the Golgi apparatus,” not low levels of dopamine.
(B) While a missing or malfunctioning gene may explain why levels of alpha synuclein have risen to toxic levels in the cell, it does not explain why these high levels cause the cell to die.
(C) The effectiveness or ineffectiveness of drug therapy in yeast cells does not explain why high levels of alpha-synuclein would kill the cell. Furthermore, the fourth
paragraph suggests that drug therapy actually has been effective in yeast cells, not to mention in fruitflies, roundworms, and cultures of rat neurons.
(D) CORRECT. The second paragraph states that high levels of alpha-synuclein “disrupt the flow of proteins from the endoplasmic reticulum…to the Golgi
apparatus.” According to the passage, the Golgi apparatus is responsible for distributing proteins within the cell. It also states that "when the smooth transfer of
proteins from the endoplasmic reticulum to the Golgi apparatus is interrupted, the cell dies."
(E) The passage gives no indication that alpha-synuclein is “by nature” a toxic substance. Rather, the passage states that high levels of alpha-synuclein are toxic to
the cell.

3.
This is a specific question. We can use the key phrase “current treatments of Parkinson’s Disease” from the question to help us locate the relevant portion of the passage. The first paragraph discusses current treatments.
(A) Current treatments do not repair damaged cells. Rather, they “are primarily reactionary, aiming to replenish dopamine levels after dopamine-producing neurons
in the brain have died.”
(B) The passage does not discuss the effectiveness of current treatments.
(C) CORRECT. The first paragraph states that current treatments “replenish dopamine levels after dopamine-producing neurons in the brain have died.” It goes on to say that “without a more detailed understanding of the behavior of dopamineproducing neurons, it has been impossible to develop treatments that would prevent the destruction of these neurons in Parkinson’s patients.” We can therefore conclude that current treatments are based on an incomplete understanding of the dopamin eproducing
neuron.
(D) While the passage gives hope that new drug therapy will be effective, the fourth paragraph introduces the possibility that such treatments won’t be transferable to humans: “researchers are hesitant to conclude that such therapies will prove successful on human patients.” Thus, the claim that current treatments will inevitably be replaced by new drug therapy is unsupported by the passage.
(E) There is no information in the passage on the methods used to develop current treatments. It is very possible that yeast cells were used in researching current treatments.

4.
The second paragraph states that “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.” This implies that proteins in healthy cells are produced in the endoplasmic reticulum, sent to the Golgi
apparatus where they are modified, and then shipped to the rest of the cell.
(A) CORRECT. This chronology is supported by the information given in the second paragraph.
(B) Proteins are created in the endoplasmic reticulum, not the Golgi apparatus. Further, there is no evidence to show that proteins in healthy cells are decomposed
by alpha-synuclein.
(C) There is no evidence to show that proteins in healthy cells are decomposed by alpha-synuclein.
(D) Proteins are created in the endoplasmic reticulum, not the Golgi apparatus.
(E) Proteins are created in the endoplasmic reticulum, not by alpha-synuclein.