Reading Comprehension

PT145 · S1 · P4 · Q26 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.

26.

Which one of the following, if true, would most strengthen the position attributed to Steele and his colleagues in the passage?

  1. Correct

    Scientists have succeeded in altering

    Why this is right

    This buttresses the claims being made in the 3rd paragraph by "Steele and company". They believe it's possible for a virus to transport altered DNA into the reproductive DNA. This answer gives us an example of a virus carrying new DNA to reproductive cells and changing them! It looks like they were right. It is possible.

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

    62% picked this

  2. The patterns of mutations found

    Out of Scope: nervous system

    Steele and colleagues didn't make any claims about the nervous system. It's not clear why the "signature" pattern of mutations appearing in the nervous system makes it any more likely that this pattern indicates that DNA has been transferred into reproductive organs.

    6% picked this

  3. The process by which the

    No Impact

    We were already assuming it was trial and error, since mutations don't have any intelligence or goal-oriented behavior. So, this barely feels like new information, and it doesn't help us believe that viruses can transmit altered DNA into reproductive DNA, or that the "signature" pattern of mutations in immune system genes means that in the past DNA has been transferred to the reproductive organs.

    1% picked this

  4. Fossil remains show that giraffes

    No Impact

    We know that giraffes gradually evolved with long necks. The Lamarckian explanation is that "by stretching during their lifetimes, they elongated their necks and passed on that trait to their offspring". The accepted Darwinian explanation is that "the giraffes with longer necks were more likely to survive and have babies, so the trait of longer necks was naturally selected for". The fact that giraffes have long necks doesn't answer the question of how they evolved those long necks.

    4% picked this

  5. It is known that birds

    Yolk Sac vs. DNA

    This is very close to usable, but Steele & Co. are trying to establish that you can pass on acquired immunities to reproductive DNA. A chick gestating in a yolk sac is similar to a fetus gestating in a mother's womb. Both the chick and the fetus already have their DNA at the point they're gestating. Moms pass on acquired immunities via their placenta and via their breastmilk (once the babies are born). That's not the same as the kid having DNA that was changed by the mom acquiring an immunity. The kid is picking up antibodies from the placenta. The chick is picking up antibodies from the yolk sac. But Steele & Co are positing that the kid / chick could actually be picking up acquired immunities via their DNA.

    27% picked this

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