Reading Comprehension

PT145 · S1 · P4 · Q21 Genetic Typos

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The French biologist Jean-Baptiste de Lamarck (1744–1829) outlined a theory of evolutionary change in 1809, 50 years before Darwin’s On the Origin of Species.

Topic

The revival of Lamarckian evolutionary theory through new research on heredity in the immune system.

Framework

Old / New; Present Debate

Main Point

Edward J. Steele and his team are challenging the widely dismissed Lamarckian theory of evolution by proposing that a mechanism in the immune system could allow acquired traits to be inherited, although most biologists remain skeptical due to lack of direct evidence. ( — End of P1 gives the core new idea, while P4 presents ongoing skepticism and the debate.)

P1: Introduction to Lamarck and Steele's Revival

Lamarck, a French biologist, suggested in 1809 that organisms could inherit traits acquired during their lifetimes. While this idea has been mostly laughed off by modern biologists, Edward J. Steele is now trying to bring Lamarckism back, claiming he’s found supporting evidence in how our immune system works.

P2: The Immune System’s Mutating Genes

This paragraph lays out the mystery of how the immune system adapts so quickly to new threats—partly by certain cells mutating their genes at an unusually high rate, creating "typos" as the DNA is copied to RNA. This enables the immune system to experiment with defenses on the fly.

P3: Steele’s Lamarckian Hypothesis and Its Mechanism

Here we get the details of Steele’s theory: he proposes that altered RNA is turned back into DNA (a process called "reverse transcription"), and suggests that viruses could carry this altered DNA into reproductive cells—potentially passing acquired traits to offspring.

21.

The author most likely calls a certain kind of mutation a "typo" (second-to-last sentence of the second paragraph) primarily in order to

  1. distinguish it from mutations that

    Wrong Purpose: distinguish from adaptive

    All mutations are random, and we designate them as "adaptive" if they have survival value for the organism in that organism's environment. It sounds like some of these typos end up being the right fit to "do the job" against a novel disease, so those typos would be adaptive mutations.

    12% picked this

  2. characterize it as relatively inconsequential

    Opposite, if anything: inconsequential

    While a "typo" in an email might be an inconsequential mistake, the passage is suggesting the opposite here. Some of these genetic typos are allowing the immune system to craft an effective defense against a new disease. That sounds like a pretty consequential typo!

    6% picked this

  3. Correct

    indicate that it is an

    Why this is right

    This answer seems to obvious and literal that it feels dangerous to pick it, but it's definitely accurate. A cell's DNA is being transcribed into RNA (i.e. copied onto a different medium) but a mutation is causing an imperfect copy. The variation caused by the imperfect copying is how the immune system can "learn" to fight a new disease it didn't already have "knowledge" of, coded in its genes.

    Skill tested: Local Purpose · how this choice captures the passage's function is the move to repeat next time.

    76% picked this

  4. emphasize that it is easily

    Not Emphasized: easily overlooked

    While a "typo" in an email might be easily overlooked, the author isn't stressing any such thing here. The author is explaining how the immune system can defend against new diseases.

    2% picked this

  5. suggest an analogy between scientific

    Dictionary Trap

    This is playing too literally off the traditional sense of "typo", when we're writing or typing something. Nothing in the passage is discussing "textual analysis", or proposing that scientific investigation is similar to analyzing texts. The author is only talking about "typos" because she's explaining how mutations allow the immune system to deal with new diseases.

    4% picked this

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