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A geneticist is studying a newly discovered gene (Gene X) that is hypothesized to influence plant height. They perform an experiment where they cultivate two groups of a genetically identical plant species under identical environmental conditions. Group A plants have a functional Gene X, while Group B plants have a 'knockout' (non-functional) version of Gene X. After 8 weeks, they measure the average height of plants in both groups. Which of the following best describes the role of Group A in this experimental design?
- AIt serves as the experimental group, demonstrating the effect of the non-functional gene.
- BIt acts as a positive control group, confirming the expected outcome if the gene is functional.
- CIt acts as a negative control group, showing the baseline height with a functional gene.
- DIt is the independent variable, representing the presence of the functional gene.
Show answer & explanationAnswer & explanation
Correct answer: C. It acts as a negative control group, showing the baseline height with a functional gene.
Group A, with a functional Gene X, represents the normal or unmanipulated state. It provides a baseline against which the effects of the non-functional gene (in Group B, the experimental group) can be compared. This makes it a negative control.
Why the other options are wrong
- A. Group B (non-functional gene) is the experimental group; Group A is the control.
- B. A positive control would typically be a group where a known effect is expected to ensure the experimental setup is working, which isn't the primary role here.
- D. The independent variable is the gene's functionality (functional vs. non-functional), not the group itself.
Negative Control
An experimental control that does not receive the treatment or manipulation being tested and is expected to show no change or a baseline outcome. It helps to ensure that no unmeasured variables are causing an effect.
- Does not receive the experimental treatment.
- Expected to produce no effect or a baseline result.
- Used to rule out confounding factors and confirm the specificity of the treatment effect.
Memory trick: Controls Guide Results' Truth