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
The author elaborates on the idea that creating a full analysis of platypus DNA was an important scientific endeavor mainly through
- Aa description of the type of information about human genetics that specialized research can yield.
- Ba comparison of the platypus with its closest bird and reptile relatives on the evolutionary tree.
- Cthe discussion of how unusual the platypus genome is in the animal kingdom.
- Dthe explanation of how genetics can be aligned to physiological function.
Show the answer
Correct answer: A
The question asks how the author elaborates on the idea that creating a full analysis of platypus DNA was an important scientific endeavor.
A. CORRECT. The importance of the research into platypus DNA is explained in the excerpt through descriptions of what this research can teach us about human genetics and disease. The question is raised directly in paragraph 4 and begins to be answered in paragraph 6 (“The platypus genome results . . . 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”). This importance is also addressed in the “Same and Different” section (paragraphs 9–11) and in paragraphs 15 and 16.
B. Incorrect. The comparison of the platypus with its bird and reptile relatives in paragraphs 12–15 is important to locating the platypus on its evolutionary family tree and in showing the connection between DNA and functionality. This comparison does not, however, explain the excerpt’s main reason for asserting that the analysis of platypus DNA was an important scientific endeavor.
C. Incorrect. Although the excerpt mentions that part of the platypus’s appeal is its “cuteness and weirdness” (paragraph 2) and describes it as having a “patchwork of genes” (paragraph 2), the scientific importance of analyzing the platypus genome is not derived from its unusualness but rather from its ability to shed light on the human genome through comparative genomics (“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” [paragraph 17]).
D. Incorrect. The excerpt briefly explains the connection between genes and some of the platypus’s physiological functions, such as producing milk and venom (paragraphs 13 and 14). Although paragraph 15 mentions the scientific value of understanding these genetic connections (“Such investigations may help medical researchers understand health issues related to reproduction and lactation”), paragraph 16 indicates that there is even greater value in studying the platypus genome through comparative genomics (“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”). The full analysis of the platypus DNA was an important scientific endeavor primarily because it furthers the ability of scientists to understand “millions of years of evolution” and offers “vital information to understanding the role of genes in the health and disease of mammals like us” (paragraph 18). The discussion of physiological function itself is not the real importance of the scientific endeavor.
Question analysis
This question asks how the author of “Research Riddle Resolved” mainly elaborates on the idea that a full analysis of platypus DNA was an important scientific undertaking. Students must look across the whole 18-paragraph excerpt and decide which kind of content does most to show the work’s value, since the article mixes several kinds of detail about the platypus and its genes.
- Grade level
- Grade 8 reading and task
- Compared with grade 7
- Above grade 7 Grade 7 students trace how an author supports an idea, usually within a few paragraphs. This question spans an 18-paragraph technical excerpt, and the choices name kinds of content that all appear in it, so students must judge which one carries the most weight.
- Estimated difficulty
- Hard: combines ideas, needs a plan, and has more than one tempting wrong answer.
- Thinking it demands
- Depth of knowledge 3, strategic thinking · mainly evaluate
- What makes it hard
- A very close wrong answer moderate
- Evidence in several places moderate
- The right answer is reworded moderate
- Evidence
- Answered from the whole text
- Reading level
- Passage: about grade 11, 809 words; question and choices: about grade 12, 76 words.
- 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
Every choice names something the excerpt really contains, so the question is one of weight: which kind of content carries the case that the platypus work mattered. The physiological-function choice is hardest to reject because paragraph 15 says outright that its “scientific value … is high,” yet paragraph 16 widens the point with “More generally, though.” Students who list each place the article explains the research’s value find most of them pointing to what it teaches about human genes and health.
A very close wrong answer moderate Choosing the answer
The physiological-function choice is a real case of the key’s idea, paragraph 15’s milk production and “health issues related to reproduction and lactation”; the key names the broader kind of knowledge the excerpt keeps returning to. (Embretson & Wetzel, 1987; Gorin & Embretson, 2006; Ascalon et al., 2007)
Evidence in several places moderate Working it out
The value of the work is argued in pieces, the question of paragraph 4, human genes in paragraphs 7–11 and the health payoffs of paragraphs 15–18, and must be gathered before “mainly” can be judged. (Kirsch & Mosenthal, 1990; Gorin & Embretson, 2006)
The right answer is reworded moderate Choosing the answer
The key’s “type of information about human genetics” uses none of the article’s phrases, while a wrong choice repeats paragraph 15’s “genetics to physiological function” almost word for word. (Freedle & Kostin, 1993; Kirsch & Mosenthal, 1990)
Strategy: Find each place where the article says why the platypus research matters, note what kind of reason each one gives, and choose the option that fits most of them rather than a single paragraph.
Traps
- Supports only part of the claim: In a question about evidence: a line that backs one half of the claim but not the other, or a related point rather than the claim itself.
- Wrong purpose or structure: Names a purpose, structure or effect that the part does not serve, or describes what a part says when the question asks what it does.
- True but not the answer: A choice says something accurate about the text that does not answer this question.
The wrong answers, classified
B True but not the answer (King et al., 2004; Embretson & Wetzel, 1987)
Recalls the yolk, milk and venom comparisons of paragraphs 12–14, which open the “Chicken or Egg?” section, but they trace where the platypus came from rather than why decoding its DNA mattered.
C Wrong purpose or structure (Anderson & Krathwohl, 2001)
Takes the platypus’s oddness, the hook of the opening, as the reason the work mattered, though paragraph 6 calls the results “far more than confirmation of a scientific oddity.”
D Supports only part of the claim (King et al., 2004; Thissen, Steinberg & Fitzpatrick, 1989)
Is drawn by paragraph 15’s “scientific value … is high,” but linking genes to milk production is one example, and paragraph 16 widens the point to “health and disease risk.”
Working it out, step by step
Figure out what the question asks
This asks how the author mainly shows that studying platypus DNA was important. An endeavor is a serious effort or project. Every choice names something that is really in the excerpt. So you must decide which one the author uses most.
List where the author explains the value
- Paragraph 4 asks what platypus DNA can “tell us about people and the diseases we get.”
- Paragraph 11 says comparing genes may lead to “ways to understand, treat, and prevent human diseases.”
- Paragraph 16 says the work shows “how genetic changes relate to health and disease risk.”
- Paragraph 18 says it gives “vital information to understanding the role of genes in the health and disease of mammals like us.”
Find the pattern
Again and again, the author says the research teaches us about human genes and health. That is the kind of information this research can yield, or give. So that is the author’s main support.
Check each choice
- A fits. The author keeps describing what the research can teach about human genes and disease.
- B does not fit. The comparisons with chickens, snakes and lizards in paragraphs 12–14 show where the platypus came from. They do not explain why the study mattered.
- C does not fit. Paragraph 6 says the results are “far more than confirmation of a scientific oddity.” The oddness is not the main reason.
- D does not fit. Physiological function means how a body works, like making milk. Paragraph 15 gives this as one example. Then paragraph 16 widens the point.
Watch out: D is tempting because paragraph 15 says the “scientific value of pinning genetics to physiological function” is high. But that is one case of the bigger idea.
Choose the answer
The author mainly shows the value of the research by describing what it can teach about human genes and health. So the answer is A.
Why this answer and not the closest wrong one
D is the closest wrong choice. Linking genes to making milk is a real example of the research’s value. But paragraph 16 begins “More generally, though,” and widens the point to “health and disease risk.” Most of the excerpt’s reasons are about human genes and health. That broader kind of information is A.
More questions like this
The original DOE question
The passage “Excerpt from “Research Riddle Resolved”” as printed (pages 66–67)
