Susan is a microbiologist studying Yersinia pestis using a mouse model of infect
ID: 267499 • Letter: S
Question
Susan is a microbiologist studying Yersinia pestis using a mouse model of infection. She makes an educated guess that a particular Yersinia pestis gene (let's call it 'Gene X') may encode a virulence factor. She makes a mutant strain that lacks gene X. In the mouse infection model this mutant strain has an equivalent Lethal Dose 50% (LD50) compared to the 'wild-type' strain (that possess a normal Gene X). Based on this finding, what can Susan conclude?
A) Gene X encodes a virulence factor (at least by this method of testing).
B) Gene X does not encode a virulence factor (at least by this method of testing).
C) There is not enough information to decide if Gene X encodes a virulence factor.
D) Susan was mistaken to think that LD50 measurements have anything to do with virulence factors.
Please explain why! thank you
Explanation / Answer
The answer is A) Gene X encodes a virulence factor (at least by this method of testing).
Virulence is the ability to cause disease and can be determined quantitatively by measuring lethal dose (LD), 50%.The LD50 indicates the number of microorganisms required to kill 50% of a population infected with a particular microbe. So and organism that has a low LD50 is more virulent as fewer number of these bacteria are required to cause infection. In this case, the mutant strain that lacks gene X has a higher LD50, meaning that more of these mutant microbes are required to cause an infection. This suggests that gene X encodes a virulence factor, as the presence of it causes the wildtype strain to have a lower LD50..
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