Passage Excerpt from “Research Riddle Resolved”
Excerpt from “Research Riddle Resolved”
For centuries, scientists were confounded by an animal that seemed to look and act like a combination of a bird, a reptile, and a mammal. It has a bill like a duck and lays eggs but produces milk for its young. It lives in a burrow, has fur, and can make venom. We now know that this animal is called a duck-billed platypus. A platypus is a monotreme, a type of egg-laying mammal.
Hundreds of years after the first sightings of the platypus, the animal still captures our imagination anew and irresistibly attracts the attention of science writers everywhere. The May 2008 Nature report detailing the DNA insides of the duck-billed platypus invited colorful tales from just about every mainstream media outlet.
But cuteness and weirdness aside, the platypus research results are a gold mine for medical researchers. The findings cement what may have seemed totally obvious but turned out to be a bit of a scientific surprise: platypus DNA is a patchwork of genes from reptiles, birds, and mammals.
Evolution Fusion
In other words, the platypus heritage is laid out in an evolutionary DNA tapestry that marks the time, hundreds of millions of years ago, when reptiles and mammals branched off the evolutionary tree.
So what? The platypus is nothing like a human, so what can its DNA tell us about people and the diseases we get?
Plenty, says an international team of scientists who did this work.
The platypus genome results are far more than confirmation of a scientific oddity. They provide researchers a window into a time in history when mammals became unique—gaining the ability to bear live young, produce milk for them, and grow a warm, furry coat.
That’s important because our own, modern-day genomes are still a big mystery and researchers need much more information to be able to translate our genetic language into useful health knowledge.
One of the ways scientists can decipher meaning from within our 3 billion DNA “letters,” or nucleotides, is to compare human genes with those from animals, to see what has been kept the same and what has evolved to be different. . . .
Same and Different
In an approach called comparative genomics, scientists compare the genome sequences of several species: human, mouse, and a wide variety of other organisms from single-celled fungi to elephants and, now, the platypus.
The goal of this research is to find regions of similarity and difference in order to better understand the structure and function of human genes.
Comparative genomics is directly related to evolution because all living things share a common ancestor. By using computer tools to examine genes that have been kept the same in many organisms over millions of years, researchers can locate signals that control how genes work. This information may translate into ways to understand, treat, and prevent human diseases. . . .
Chicken or Egg?
When researchers analyzed platypus DNA and compared it to that of chickens, snakes, and lizards, the findings traced the evolutionary path from birds and reptiles to mammals. They learned that the platypus lost most of its genetic ability to produce egg yolk—as compared to chicken genes. This suggests its departure from “chicken-ness.”
But, through evolutionary change, the platypus gained the ability to make milk that is rich in nutrients. Platypuses have genes that make the milk protein casein: just like we do.
A male platypus can, like its ancestral snake and lizard cousins, produce venom. The platypus ejects this venom through special glands in its back legs. The evolutionary reason for maintaining such molecular weaponry isn’t yet clear, but what is fascinating is that it appears nature mixed and matched together DNA pieces separately to create the venom genes in reptiles and monotremes like the platypus.
The scientific value of pinning genetics to physiological function—like milk production—is high. Such investigations may help medical researchers understand health issues related to reproduction and lactation. Although lactation is an ancient reproductive trait, mammals—including the platypus—are unique in their ability to produce milk that is extraordinarily nutritious, containing a rich blend of sugars, fats, and proteins.
More generally, though, studying how nature cuts and pastes gene modules gives scientists an inside scoop on how genetic changes relate to health and disease risk.
One thing is clear—the stunning blend of reptile, bird, and mammal puts the platypus in a class of its own, and it gives researchers much more: information about how mammals like us came about.
[Scientists’] genetic sleuthing of platypuses, chimps, fish, sunflowers—you name it—continues to teach scientists how millions of years of evolution progressed. This provides vital information to understanding the role of genes in the health and disease of mammals like us and our pets, and can also help preserve our rich and diverse planet.
From “Research Riddle Resolved”—Public Domain/National Institutes of Health
Question
How can researching the genomes of other animals inform scientists’ understanding of human health and disease?
- ATracking how other animals evolved over millions of years helps researchers preserve and sustain nature.
- BFinding ways that animal genomes are similar to the human genome helps researchers find signals that control genes.
- CObserving that all living things evolved from a common ancestor helps researchers pinpoint certain genetic traits.
- DUnderstanding how other animals are similar to one another helps researchers understand how humans evolved.
Show the answer
Correct answer: B
The question asks how researching the genomes of other animals can inform scientists’ understanding of human health and disease.
A. Incorrect. Although tracking how other animals evolved helps researchers better understand our “rich and diverse planet” (paragraph 18) through understanding genes, the potential benefits to human health will not necessarily preserve or sustain nature.
B. CORRECT. Paragraph 11 explains that finding ways that animal genomes are similar to the human genome helps researchers “locate signals that control how genes work.”
C. Incorrect. While paragraph 11 does point out that all living things share an ancestor, the idea that they, therefore, share genetic traits is only implied. This idea does not contribute to the main focus of the research.
D. Incorrect. The statement that “understanding how other animals are similar to one another helps researchers understand how humans evolved” is too general to provide support for the main focus of the genetic research described in the excerpt. To learn more about human health and disease, scientists need to understand the similarities between the genetic material of different animal species. These scientists are interested in learning more about issues that currently affect humans, not only understanding their evolutionary history.
Question analysis
This key-details question on “Research Riddle Resolved” asks how studying the genomes of other animals can help scientists understand human health and disease. The question names no paragraph, so students must find where the article explains this link and recognize that explanation in a choice, while every option sounds scientific and must be checked against the text.
- Grade level
- Grade 7 reading and task
- Compared with grade 7
- At grade 7 Finding an explained detail in an informational text is routine grade 7 work. The demand comes mostly from the article’s technical wording and from locating the right paragraph without a reference, not from any inference.
- Estimated difficulty
- Straightforward: two steps or one careful reading.
- Thinking it demands
- Depth of knowledge 2, skills and concepts · mainly understand
- What makes it hard
- Evidence in several places minor
- An unfamiliar subject minor
- Evidence
- Answered from one paragraph or stanza
- Reading level
- Passage: about grade 11, 809 words; question and choices: about grade 12, 80 words.
- Corrected from the DOE handbook
- An overstatement in the explanation was corrected.
- Students, last 30 days
- Not enough answers yet to show (it takes 10).
Why it is hard, traps and wrong answers (shows the answer)
Why it is hard
The answer is stated in one sentence of paragraph 11, so the work is finding it and recognizing it reworded. Two wrong choices also come from the article, the common ancestor in the same paragraph and the closing hope of preserving the planet, and they tempt students who stop at familiar words. Checking which choice names the step that comes just before “This information may translate into ways to understand, treat, and prevent human diseases” settles it.
Evidence in several places minor Working it out
Health and disease come up in paragraphs 4, 7, 11, 15, 16 and 18, but only paragraph 11 explains how comparing genomes leads there, through “signals that control how genes work.” (Kirsch & Mosenthal, 1990; Gorin & Embretson, 2006)
An unfamiliar subject minor Understanding the question
Paragraph 11 explains the link in technical terms, genes “kept the same in many organisms” and signals that control genes, which students must follow without knowing what such signals are. (Recht & Leslie, 1988; Kintsch, 1998)
Strategy: Scan the excerpt for the places that tie gene research to human disease, reread them closely, and choose the option that restates the step they describe rather than just reusing their words.
Traps
- Word match: Repeats striking words or phrases from the text, so it looks supported, but its meaning does not fit the question.
- Twists what the text says: Uses the text's topic and ideas but changes what it says: who did it, how much, when, or why.
- True but not the answer: A choice says something accurate about the text that does not answer this question.
The wrong answers, classified
A True but not the answer (King et al., 2004; Embretson & Wetzel, 1987)
Borrows paragraph 18’s closing remark that gene research can help preserve the planet, which the article does say, but it concerns nature, not human health or disease.
C Word match (Freedle & Kostin, 1993)
Picks up paragraph 11’s “all living things share a common ancestor,” the reason comparing genes works, and makes that observation the tool, though the paragraph credits examining genes kept the same.
D Twists what the text says (King et al., 2004)
Swaps comparisons with human genes for animals compared with each other, and health for how humans evolved, a theme paragraphs 17 and 18 touch but not the question’s link to disease.
What was corrected from the DOE handbook, and why
- Explanation: The handbook’s explanation of Option D says the scientists “are interested in learning more about issues that currently affect humans, not understanding their evolutionary history.” The excerpt says the platypus results give researchers “a window into a time in history when mammals became unique” (paragraph 6) and “information about how mammals like us came about” (paragraph 17), so the site now says “not only understanding their evolutionary history.” Option D is still wrong: it is about how animals are similar to one another and how humans evolved, not about human health and disease.
Working it out, step by step
Figure out what the question asks
This asks how studying the genomes of other animals helps scientists understand human health and disease. A genome is all the genes of a living thing. No paragraph is named, so you must find where the excerpt explains this link.
Find the paragraph that explains it
Paragraph 11 explains it: “By using computer tools to examine genes that have been kept the same in many organisms over millions of years, researchers can locate signals that control how genes work. This information may translate into ways to understand, treat, and prevent human diseases.” An organism is any living thing.
Put it in plain words
Some genes have stayed the same in many living things for millions of years. Scientists compare genomes to find those genes. The genes that match help them find the signals that control how genes work. Knowing those signals may lead to ways to treat disease.
Check each choice
- A does not fit. Paragraph 18 does mention helping “preserve our rich and diverse planet.” But that is about nature, not human health.
- B fits. Finding genes that animals share with humans helps researchers find the signals that control genes.
- C does not fit. Paragraph 11 says “all living things share a common ancestor,” a relative from long ago. That is why comparing works. It is not the step that leads to health.
- D does not fit. It compares animals with one another, not with humans. It is also about how humans evolved, not about disease.
Watch out: C reuses words from paragraph 11, so it looks right. But it skips the key step, finding the signals.
Choose the answer
Shared genes lead to the signals, and the signals may lead to ways to treat disease. So the answer is B.
Why this answer and not the closest wrong one
C is the closest wrong choice. It uses a true fact from paragraph 11, the common ancestor. But that fact only explains why comparing genes makes sense. The step that helps health is finding “signals that control how genes work.” B names that step.
More questions like this
The original DOE question
The passage “Excerpt from “Research Riddle Resolved”” as printed (pages 66–67)
