Genetic Typos

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

TopicsParagraph 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

Paragraph 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

24.

What is the primary function of the last paragraph in the structure of the passage

Answer choices

Too Narrow17% picked this
to present various objections that have been raised against the neo-Lamarckian theory outlined in
Only the final two sentences raise objections. The preponderance of this paragraph is about presenting Steele's evidence for their claims.
17%
Too Strong: dismiss the theory12% picked this
to dismiss the neo-Lamarckian theory outlined in the preceding paragraphs as not being
Our author never really takes a stand. She seems inquisitive and somewhat skeptical. She definitely doesn't dismiss the theory out of hand. The last paragraph is also contradicting this answer, which says Steele's theory is not supported by evidence, because it presents Steele's evidence.
12%
Out of Scope: new findings3% picked this
to explain how the neo-Lamarckian theory outlined in the preceding paragraphs could be revised to take
This paragraph is just asking Steele for what evidence he's got for his theory. The author isn't trying to revise Steele's theory, and I have no idea what "new findings" this answer choice is referring to.
3%
Out of Scope5% picked this
to suggest several possible directions for further research regarding the neo-Lamarckian theory outlined in
Out of Scope: directions for new research Nowhere in this last paragraph does our author suggest anything. She asks a question, makes a concession as to the limits of a possible answer, provides Steele's answers, and ends with other scientists' pushback. I guess this answer choice is trying to get people to over-value the fact that other biologists said "there may be other explanations for this pattern", and it's pretending that this line was the author suggesting that a possible new research direction would be pursuing these other explanations. But this was just a quote from biologists. The author made no suggestions.
5%
Correct64% picked this
to indicate the nature of the evidence for the neo-Lamarckian theory outlined in
Why this is right
We were looking for something like "assess the evidence Steele has for his theory". To indicate the nature of the evidence is a vague phrase that can cover "what kind of evidence does he have and how compelling is it". In the 2nd sentence of this paragraph, the author indicates the type of evidence will be circumstantial. In the 3rd and 4th sentences she indicates that Steele cite a distinct pattern of mutations in the genes that carry instructions for immune system responses, as their evidence. In the last two sentences, we learn that this evidence is not seen as very compelling by other biologists, since they think it could be interpreted different ways.
Skill tested: Paragraph Purpose · how this choice captures the passage's function is the move to repeat next time.
64%

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