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Difficulty: EasyMain Idea and Primary Purpose

For decades, entomologists attributed the biological divergence between queen and worker honeybees (Apis mellifera) exclusively to qualitative nutritional differences during larval development, specifically the continuous consumption of royal jelly by queen-destined larvae. However, recent genomic investigations have reframed this developmental bifurcation as an epigenetic phenomenon governed by differential gene expression rather than structural genomic alterations. Researchers demonstrated that silencing the enzyme DNA methyltransferase 3 (Dnmt3) in newly hatched larvae replicates the phenotypical effects of royal jelly, producing functional queens even when larvae are fed a standard worker diet. This finding reveals that royal jelly acts primarily by inhibiting Dnmt3, thereby preventing the global DNA methylation that normally represses queen-specific developmental pathways in worker larvae. Consequently, caste determination is now understood not as an irreversible genetic mandate, but as an environmentally triggered molecular switch that toggles epigenetic repression. By elucidating this pathway, recent studies have provided a concrete model for how environmental inputs directly modify the functional genome without altering underlying nucleotide sequences.

Which of the following best states the primary purpose of the passage?

  1. To present recent scientific findings that reframe honeybee caste differentiation as an epigenetically regulated process triggered by environmental inputs.Answer
  2. B
    To argue that Dnmt3 inhibition is the primary mechanism governing phenotypic plasticity across all insect species.
  3. C
    To detail the precise nutritional ingredients and chemical composition of royal jelly in larval development.
  4. D
    To demonstrate that royal jelly alters the underlying nucleotide sequences of queen bee larvae during development.
  5. E
    To criticize early entomologists for fundamentally misunderstanding the role of nutrition in insect biology.

Answer

The primary purpose of the passage is to present recent scientific findings that reframe honeybee caste differentiation as an epigenetically regulated process triggered by environmental inputs.
The correct option accurately states the central purpose of the passage, which is to explain how recent research demonstrates that honeybee caste development is governed by epigenetic mechanisms (specifically Dnmt3 inhibition) influenced by nutritional inputs.

Step-by-Step Solution

1
Analyze the structural arc of the passage.
The passage begins by describing a traditional view (caste difference caused solely by nutrition) and introduces a pivot ('However') to present new genomic research showing caste determination is an epigenetic process controlled by Dnmt3 inhibition.
Identifying structural transitions highlights the author's main point and purpose.
2
Evaluate the central thesis of the author.
The author concludes that caste determination is an environmentally triggered molecular switch that modifies gene expression without altering DNA sequences.
The primary purpose must encapsulate the central argument rather than specific supporting details.
3
Eliminate options with scope, tone, or extrapolation errors.
The correct option captures the main claim accurately, while wrong options extrapolate to all insects, focus on narrow nutritional details, misstate factual claims about DNA alteration, or mischaracterize the tone as critical.
Ensures the selected answer is both accurate and comprehensive.

Key Concept

Identifying the Primary Purpose in Reading Comprehension
Estimated Time:1m 0s
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Topics

Main Idea and Primary Purpose

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