Necessary AssumptionDiff: Medium
Logic Breakdown
Passage Summary: Scientists broke one specific gene in flies, and those flies lost their UV sight. Because of this, the scientists claim that any fly without UV sight must have that exact gene broken.
Conclusion: Any fly of this species that lacks ultraviolet vision must have damage to this specific gene.
Reasoning: In an experiment, altering a single gene in cloned flies caused them to lose ultraviolet vision, while their genetically identical siblings with the unaltered gene retained normal vision.
Analysis: The argument suffers from a classic causal flaw: it assumes that because a specific gene damage *can* cause a loss of vision, it is the *only* thing that can cause it. To make this conclusion valid, the author must assume there are no other ways for a fly to lose its UV vision. When looking for a necessary assumption, look for a statement that rules out alternative causes, such as other genetic mutations or environmental factors that could also result in the loss of ultraviolet sight.
Conclusion: Any fly of this species that lacks ultraviolet vision must have damage to this specific gene.
Reasoning: In an experiment, altering a single gene in cloned flies caused them to lose ultraviolet vision, while their genetically identical siblings with the unaltered gene retained normal vision.
Analysis: The argument suffers from a classic causal flaw: it assumes that because a specific gene damage *can* cause a loss of vision, it is the *only* thing that can cause it. To make this conclusion valid, the author must assume there are no other ways for a fly to lose its UV vision. When looking for a necessary assumption, look for a statement that rules out alternative causes, such as other genetic mutations or environmental factors that could also result in the loss of ultraviolet sight.
Passage Stimulus
Passage Redacted
Unlock Full Passage10.Which one of the following is an assumption required by the argument?
Correct Answer
B
No other gene is required for forming the UV-vision cells ensures there is no alternative genetic route to lacking those cells. Negation test: if some other gene were required, then damage to that other gene could also cause a lack of UV vision even with this gene intact, directly contradicting the conclusion that any fly lacking UV vision must have damage to this gene.
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