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So I just took AAMC #7 and I have a question about the wording in one of the biology passages.
#129: "One difference between different strains of H. pylori is that they:"
A) attack different hosts
B) express different genes
C) exhibit different degrees of resistance to antibiotics
D) exist in either developed or developing countries
The passage states: "Genetic studies of H. pylori have identified genes that are expressed in different strains of this bacterium. One gene, vacA, encodes a toxin. Expression of another gene, cagA, leads to inflammation and may be related to the genesis of gastric cancer."
My first instinct is to go with B, but after re-reading the passage, the wording seemed somewhat ambiguous. I feel like the first sentence could be taken to mean that the same genes are expressed in multiple strains. So, vacA and cagA are found to be present in many different strains. But the sentence could also mean that different genes are expressed in different strains. So one strain expresses vacA and a different strain expresses cagA. This is the rationale for the correct answer, which is B.
"B) express different genes
According to the passage, there is more than one strain of H. pylori. One strain expresses the gene vacA that encodes a toxin. The other strain encodes a gene cagA that leads to inflammation and might be related to the genesis of gastric cancer. Thus, a significant difference between the strains is that the strains express different genes"
I ended up going with C, because the wording in the passage freaked me out and because the passage states that "Current treatment employs antibiotics directed against these bacteria and often is successful in eradicating persistent infections". I took the "often" to mean that some strains are resistant to antibiotics. I know thats a bit of a stretch, but like I said, B freaked me out too much.
I guess I get why the answer is B. If they are different strains, they must express different genes (Otherwise, what would make them different?). But the portion from the passage that they use for the rationale does seem like it could mean two different things.
Overall I did fairly well this one (34: 13/11/10), but this question is bugging me. Does anyone else think that the statement in the passage is ambiguous or am I just overthinking this one. Okay, I know I'm overthinking this, but it's still pretty ambiguous, right?
#129: "One difference between different strains of H. pylori is that they:"
A) attack different hosts
B) express different genes
C) exhibit different degrees of resistance to antibiotics
D) exist in either developed or developing countries
The passage states: "Genetic studies of H. pylori have identified genes that are expressed in different strains of this bacterium. One gene, vacA, encodes a toxin. Expression of another gene, cagA, leads to inflammation and may be related to the genesis of gastric cancer."
My first instinct is to go with B, but after re-reading the passage, the wording seemed somewhat ambiguous. I feel like the first sentence could be taken to mean that the same genes are expressed in multiple strains. So, vacA and cagA are found to be present in many different strains. But the sentence could also mean that different genes are expressed in different strains. So one strain expresses vacA and a different strain expresses cagA. This is the rationale for the correct answer, which is B.
"B) express different genes
According to the passage, there is more than one strain of H. pylori. One strain expresses the gene vacA that encodes a toxin. The other strain encodes a gene cagA that leads to inflammation and might be related to the genesis of gastric cancer. Thus, a significant difference between the strains is that the strains express different genes"
I ended up going with C, because the wording in the passage freaked me out and because the passage states that "Current treatment employs antibiotics directed against these bacteria and often is successful in eradicating persistent infections". I took the "often" to mean that some strains are resistant to antibiotics. I know thats a bit of a stretch, but like I said, B freaked me out too much.
I guess I get why the answer is B. If they are different strains, they must express different genes (Otherwise, what would make them different?). But the portion from the passage that they use for the rationale does seem like it could mean two different things.
Overall I did fairly well this one (34: 13/11/10), but this question is bugging me. Does anyone else think that the statement in the passage is ambiguous or am I just overthinking this one. Okay, I know I'm overthinking this, but it's still pretty ambiguous, right?
