5

Set 1: Command of Evidence (Advanced)

Explanation

Answer: A

PASSAGE

Epigenetics involves changes in gene expression that do not involve alterations to the DNA sequence. Methylation is a common mechanism where a methyl group attaches to DNA, typically repressing gene transcription. Researchers found that mice exposed to high stress showed increased methylation in genes regulating stress response.

What is the likely functional consequence of the increased methylation observed in the mice?

A. The DNA sequence of the stress genes was mutated.✓ Correct
B. The production of proteins from the stress response genes was reduced.
C. The mice became completely immune to stress.
D. The methyl groups caused the DNA to replicate faster.

Detailed Explanation

The text states methylation 'typically repressing gene transcription'. Transcription leads to protein production. If transcription is repressed (reduced), then protein production is reduced.

Key Evidence:

• "typically repressing gene transcription"

Why others are wrong: A (Text says 'do not involve alterations to the DNA sequence'.), C (Reduced stress response often makes stress *worse*, not immune.), D (Not mentioned.).

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