PrepTest 141, Section 3, Question 4
An organism is considered to have an infection(446 more words not shown)
Which one of the following(7 more words not shown)
- AThe only way(22 more words not shown)
- BMost infectious diseases(16 more words not shown)
- CIf they were(11 more words not shown)
- DAlzheimer's disease and(15 more words not shown)
- EPrion diseases generally(10 more words not shown)
Reading the passage
The chain reaction is doing the damage: abnormally shaped prions cause other prions to change shape, the cascade produces plaque, and the plaque destroys nerve cells. The opening also says an agent must be able to reproduce to establish an infection.
What we’re looking for
That supports a clear inference. If we remove the ability to reproduce, we break the process that explains CJD. A lone abnormal protein isn't the self-propagating cascade described in the account.
Working the answers
- A
We aren't told how CJD is transmitted between people. Specifying injection as the only route adds both a mechanism and an exclusivity claim.
- B
Discovering another class of pathogens doesn't mean most diseases previously attributed to other agents have been reassigned to prions. No such sweeping revision is described.
- CCorrect
Without reproduction, the abnormal prions couldn't initiate the accumulating chain reaction responsible for the damaging plaque. This follows from the infection requirement and the specific account of CJD's development.
- D
The last paragraph says a similar process may be involved in Alzheimer's and Parkinson's. It doesn't establish that they are caused by different forms of the same pathogen. A possible connection has become a definite, more specific claim.
- E
No comparison ranks prion diseases against other infectious diseases by aggressiveness. The variation described is among cases of CJD, not a contest between classes of pathogens.
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