Reading ComprehensionDifficulty: Medium

PT145 S1 P4 Q23 Explanation

Genetic Typos

A free, expert breakdown of this official LSAT Reading Comprehension question.

TopicsPrimary PurposeScience

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Passage

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. Lamarck’s basic idea was that organisms change in adapting to their environment and then pass on to their offspring the new characteristics they have acquired. Since then, Lamarck his colleagues claim to have found evidence for a Lamarckian hereditary mechanism in the immune system.

The immune system is an evolutionary puzzle in its own right: How is it that our bodies can quickly respond to so many different kinds of attacks? Is all this information in the genes? If so, then how does our immune system defend against new diseases? Part of the answer comes from the immune system to test out different defenses until it finds one that does the job.

Steele hypothesizes that the altered RNA then reverts back into DNA. Indeed, such “reverse transcription” of RNA back into DNA has been observed frequently in other contexts. But the troublesome question for Lamarckians is this: Could this new DNA then be carried to the reproductive genes (in the sperm and egg cells), could carry the altered DNA to the reproductive cells and replace the DNA in those cells.

But even if the process Steele and his colleagues describe is possible, does it ever actually occur? Evolutionary mechanisms are never observed directly, so we must make do with circumstantial evidence. Steele and his colleagues claim to have found such evidence, namely a “signature” of past events that is “written all over” suggest there may be other, less radical explanations for the pattern of mutations that Steele cites.

What this question is testing

Primary Purpose

Your task

Pin down exactly what the question asks about the passage — a detail, the author's view, the structure, or the main point — before looking at the choices.

Common trap

Answers that restate a true detail from the passage but don't answer the specific question being asked.

Winning move

Anticipate the answer in your own words from the passage, then find the choice that matches that prediction.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
23.

The passage is primarily concerned

Answer choices

  1. Opposite1% picked this

    offering a historical account of the development of an

    This is not primarily about the Old history, it's about the New claims from Steele and his colleagues. This answer is playing the trap answer game of leaning too heavily on the first few sentences. The author discusses Lamarck as some warm-up context. But the Purpose Pivot in the final sentence of the 1st paragraph (but, yet, however, recently) shows us the foreground of the passage is really Steele's present day science.

  2. Correct77% picked this

    describing the efforts of a modern biologist to vindicate a long-disregarded

    Why this is right

    This works, since the "modern biologist" is Steele, and his team's research and claims are the central topic of the whole passage. Is he trying to vindicate a long-disregarded evolutionary theory? According to the thesis sentence (the final sentence of the first paragraph), he is "attempting to revive Lamarckism", and Lamarckism is definitely a long-disregarded evolutionary theory. Since 1809, when Lamarck outlined his theory, he's been ridiculed and most modern biologists are adamant that nothing of the sort he describes occurs, ever. So we can read this answer as "the passage is primarily concerned with describing the efforts of Steele to revive Lamarckism", which seems very on point.

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

  3. Wrong Emphasis: immune system4% picked this

    answering a set of questions about the immune system in light

    This answer makes it seem like this passage was primarily about the immune system, when instead it was primarily about Steele's research, which is not even alluded to in this answer choice.

  4. Wrong Emphasis: Lamarck17% picked this

    evaluating the overall merits of an evolutionary theory that has been rejected by

    The evolutionary theory that has been rejected by most modern biologists is Lamarck's evolutionary theory. So this answer makes it seem like the passage was mainly about evaluating the merits of Lamarck's theory, when in reality it was about considering Steele's attempt to revive the concept that acquired traits can be passed onto offspring.

  5. Wrong Emphasis: Lamarck1% picked this

    presenting a discredited evolutionary theory as a case study in the

    The evolutionary theory that has been discredited is Lamarck's evolutionary theory. So this answer makes it seem like the passage was mainly about presenting Lamarck's theory as a case study in the philosophy of science, but the main topic was actually Steele's new claims that he's found evidence in the immune system for a way that we could pass acquired traits to our offspring.

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