Reading Comprehension

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.

One function of the third paragraph of the passage is to

highlight the many similarities between yeast cells and mammalian nerve cells

explain in detail the methods used to conduct a genetic screen in yeast cells

further explain the roles of various cellular components of yeast cells

identify the genes in yeast cells and mammalian nerve cells that work to reverse the toxic levels of alpha-synuclein

clarify the relevance of genetic testing in yeast cells to the search for a new treatment for Parkinson's disease

OA - E

I picked D thinking genes in yeast cells and mamalian nerve cells might mean - 1 gene in each of the 2 . Where am I wrong ?

Thanks Stacey ...this is an eye opener

and I really appreciate you teach how to take notes as well ...awesome