Students in a biology class investigated why individual house mice (Mus musculus) can differ from one another in their blood’s mature B cell concentration. The students compared wild-type mice and knockout mice, which are mice with specific genes deactivated, when mice of each type were placed in similar naturalistic environments and taken for periodic blood sampling. Finding that knockout mice with the gene Arhgap17 deactivated tended to have lower mature B cell counts than did wild-type mice, the students concluded that differences in mature B cell concentration among house mice in nature are solely attributable to variations in the level of expression of Arhgap17.
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Verbal·Information and Ideas·Command of Evidence
hardWhich finding, if true, would most directly weaken the students’ conclusion?
A
The mice with Arhgap17 deactivated were identical to the wild-type mice except with regard to mature B cell concentration.
B
The level of expression of Arhgap17 does not appear to affect the functioning of any other genes in house mice.
C
Some wild-type mice were very similar to the knockout mice with regard to mature B cell concentration but showed a wide variety of levels of expression of Arhgap17.
D
A sampling of house mice captured in natural settings shows that individual mice can differ from one another in the level of expression of Arhgap17.