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Genetics vs. Environmental Factors

Grade 7-8 | Argumentative | Source-Based

Source Lexile®: 840L-1020L

Learning Standards




Prompt: Today you will read three articles on traits and how they are affected by the environment or inherited.


  • "IQ is in the genes"
  • "What's on your genes?"
  • "Air Pollution can mess with our DNA"

Write a claim arguing if inheritance or the environment most affects an organism's traits. Within the essay use details/evidence from all three attached articles.


Be sure to include all aspects of the argumentative structure: state your claim, support claim with logical reasoning, counterclaim, rebuttal, and concluding statement.




Source 1

IQ is in the genes

Oosthoek, Sharon. Science News for Students (Nov 24, 2014).


  1. How smart you are doesn't depend on how your parents raised you, a new study concludes.
  2. Their reading to you, talking with you at the dinner table and taking an active interest in your life could make you happy. And that's important. But it won't make you smarter, says Kevin Beaver.
  3. As a criminologist, he studies the causes of crime and ways to prevent it. Beaver works at Florida State University in Tallahassee. His research team wanted to know if different parenting styles influenced a child's intelligence. After all, Beaver notes, "intelligence has been linked to crime."
  4. Previous research has suggested different types of parenting could affect a child's IQ. Short for intelligence quotient, IQ is a score that measures human intelligence.
  5. But those earlier data hadn't separated out the effect of genetics on IQ. Beaver's team wanted to know: Are children's IQ scores really affected by how their parents raised them? Or are those scores just a reflection of what genes a child inherited?
  6. To find out, the team pored over information from a study of more than 15,000 U.S. middle- and high-school students. It's called the National Longitudinal Study of Adolescent Health.
  7. Starting in the 1994-to-1995 school year, researchers had asked students a series of questions. For instance: How warm and loving are your parents? How much do you talk with them? How close do you feel to your parents? How much do you think they care about you?
  8. Students also were given a list of 10 activities. Then the questionnaire asked how many of those activities students had done with their parents in the previous week. Did they play sports together? Go shopping? Talk with each other over dinner? Watch a movie together?
  9. Students also answered questions about how permissive their parents were. For example, did their parents let them choose their own friends, choose what to watch on TV or choose for themselves when to go to bed?
  10. The researchers then gave the students a test to gauge their IQ. Called a Picture Vocabulary Test, it asked the students to link words and images. Scores on this test have been linked repeatedly to IQ. Later in life, between the ages of 18 and 26, these people were tested again.
  11. Beaver's group was especially interested in results from a group of about 220 students who had been adopted. The parents who raised them had not passed on any genes to them. So if there was a link between the students' IQs and the way their parents raised them, the researchers should see it most clearly in the adopted students' scores.
  12. But no such link emerged. Whether students reported their parents cared about them and did things with them -- or reported that they did not -- it had no impact on the their IQ. This means a person's IQ is largely the result of the genes we inherit from our biological parents.
  13. What does Beaver make of the new findings?
  14. We all have strengths and weaknesses, he says. That means some of us will have to work harder than others to do well. And in some cases, other people will always be better than us at certain things.
  15. "The key is to find what you are good at and what you enjoy." Then, he says, "Work your hardest to become the best you can be."
  16. J.C. Barnes is a criminologist who studies how genetics and the environment affect crime. He works at the University of Cincinnati in Ohio. He agrees that the new study shows parents' behavior does not affect a child's IQ. Still, he says, it's important that all parents provide a nurturing environment for their children.
  17. Parents who do this "give their child the best chance to succeed -- not because they improve the child's IQ, but because they allow the child to develop into a healthy individual," he says.



Source 2

What's on your genes?

Pochron, Sharon. Science News for Kids (Sep 21, 2011).


  1. We've all heard it before: "It's in your genes."
  2. If you're lucky, a parent or neighbor is trying to explain one of your good quirks, not one of your goofy ones. "Your father could hit the ball out of the park, too," someone might say. Or you have the same unruly curls as your mom. Thankfully, that someone hasn't heard you and your dad snore.

  3. But what if it's not in your genes. What if it's on your genes?
  4. In 1866, Gregor Mendel showed that pea plants inherit physical and other traits from their parents according to very precise laws of nature. In 1910, Thomas Hunt Morgan showed that genes exist on chromosomes, and in 1952 Martha Chase and Alfred Hershey showed that DNA within a gene carries traits from parent to child. When someone tells you, "It's in your genes," they're saying that the part of your chromosome responsible for your quirk matches that part of the chromosome on your equally quirky parent.
  5. Except when it doesn't.
  6. Imagine two mice. One looks normal. It's tiny and brown. The other is fat and has orange fur. The orange mouse not only looks weird, its weight makes it more prone to diabetes and cancer.
  7. The biggest surprise isn't the differences between these mice -- it's the similarities. The mice have the same DNA in the same order on the same chromosomes. They're genetically identical. The difference between the mice isn't in their genes; it's on them.
  8. Methyl groups -- chemical clusters each made of one carbon and three hydrogen atoms -- latch onto DNA near a gene. Methyl groups act like switches, turning a gene on or off. In the case of the fat, orange mouse, scientist Randy Jirtle and his colleagues at Duke University used methyl groups to turn off something called the Agouti (a-goo-tee) gene. How? It was pretty simple.
  9. In 2003, Jirtle fed pregnant mice a particular diet that turned off the Agouti gene in the mama mice's babies. The Agouti gene controls fur color and the feeling of fullness after eating. With the gene switched on, the baby mice grew into orange adults that could never eat enough to be satisfied. As a comparison, the scientists fed a vitamin-rich mouse diet to pregnant mice that were genetically identical to the first group. The Agouti gene was switched off in the babies of those moms who had eaten the vitamin- rich chow. Those pups developed brown fur and a feeling of fullness after eating.
  10. Same genes, different methyl patterns -- very different looking mice. Without changing the DNA in the Agouti gene, Jirtle and his colleagues showed the power of what scientists call an epigenetic change.
  11. "Epigenetic literally means 'above the genes,'" explains Jirtle. Epigenetic changes don't rewrite DNA, the genetic code. Instead, the activity of the genes is altered. Genes contain the recipe for proteins. Every time a gene is turned on, it makes its particular protein. But how much -- if any -- of the protein a gene makes and when it makes the protein can be altered by the addition or deletion of methyl groups.
  12. In October 2010, Margaret Morris and her colleagues at the University of New South Wales in Sydney, Australia, took epigenetic research a step further. She showed that babies could inherit epigenetic changes -- a scenario never before imagined by geneticists.
  13. "We asked whether the diet of the father might affect his babies," Morris said.
  14. She took a bunch of healthy, identical male rats and put half on a high-fat diet. The other half ate regular food. Males on high-fat diets became overweight and diabetic (a common complication of obesity in humans). Males on regular diets grew into normal rats. All males mated with genetically identical females who had been raised on a standard rodent diet. Later, Morris examined the daughters of these rats. Would the obese fathers' weight problems affect their offspring? Nothing learned from Mendel and his peas would make scientists expect that it would.

  15. But Mendel and his peas don't tell us about epigenetics.
  16. Morris found that none of the rat daughters developed a weight problem, which isn't surprising given what we know about standard genetics. However, daughters of fat dads did develop health problems related to obesity.
  17. "Female baby rats looked as though they were on their way to becoming diabetic. They couldn't produce enough insulin," explains Morris.
  18. Insulin is a hormone needed for the body to use glucose -- also known as blood sugar. Glucose is the body's energy source. A shortage of insulin or the body's inability to use insulin effectively causes diabetes, a very serious disease.
  19. Genetic changes clearly didn't cause the daughters' insulin problems, because the scientists had used genetically identical rats. Instead, fat dads created sperm cells with different methyl patterns on their DNA. Daughters inherited their father's epigenetic changes. And because of changes in methyl patterns on the genes, daughters also inherited their dads' health problems.
  20. Foods that our parents eat before we're born or while we're still inside the womb can affect epigenetic switches. Smoking, drinking alcohol and aging can all cause epigenetic changes too.
  21. But can behavior create epigenetic changes? Michael Meaney and his colleagues at McGill University in Montreal answered that question in 2004 with rats.
  22. Some mother rats lick their babies a lot. Other mothers ignore their babies. Different kinds of mothering cause babies to become different kinds of adults. No one thinks adult rats remember whether their mothers licked them. But research has shown that licked babies grow up to be braver in the face of stress. Ignored babies are more scared as adults.
  23. As Meaney suspected, epigenetics played a role in this difference. The scientists found distinct differences between methyl patterns in the brain cells of licked babies and those of unlicked babies. The mother's licking flipped switches on the baby's gene that shapes how rats respond to stress -- showing that the behavior of one animal can sculpt the epigenetic clay of another animal.
  24. But Meaney and his colleagues didn't stop there.
  25. The scientists believed they could flip gene switches on fearful rats, causing them to become brave. And in 2007, the scientists discovered they were right. By injecting a chemical into rats, the scientists wiped out the animals' methyl markers and changed rat behavior. Scared rats became brave.
  26. The ability to chemically flip methyl switches can help treat human diseases. For instance, doctors can cure specific forms of leukemia (cancer of the blood or bone marrow) by using chemicals to flip methyl switches. Other scientists, including Randy Jirtle, are exploring the role of epigenetics in diseases like schizophrenia (an illness marked by deterioration of the thought processes), depression (an illness characterized by a feeling of such sadness that the sufferer can't live a normal life) and autism (an illness that makes it difficult to communicate with other people).
  27. Jirtle explains, "I want to find the genes in humans that are involved in brain development, which, as a consequence, are involved in just about every neurological disorder we have." And once Jirtle finds the genes, he'll look for the methyl groups that affect them. He believes he may find cures this way.
  28. So why are gene switches so flippable? Maybe the answer lies in common sense rather than in lab studies. Think of this: Environments change constantly -- forests change to grasslands, and grasslands change to deserts. Environments within and around our cells change, thanks to parasites and viruses. Social environments change too: A nurturing environment can become hostile with a stroke of bad luck. No matter how we look at it, humans and other organisms live in constantly changing environments.
  29. On the other hand, an organism's genome -- or set of genetic instructions -- doesn't change quickly. For example, humans now look a lot like humans from 200,000 years ago, even though parents pass on a jumbled mixture of genes to their offspring. How does something as steady as a genome cope with something as changeable as the environment? Perhaps epigenetics is the answer.
  30. Moshe Szyf at McGill University says that epigenetics may offer a way to help our unchanging genes cope with sudden changes in their, or our, environment.
  31. Changing what's on our genes appears to be easier than changing what's in them. And that may help explain how life so readily adapts to our ever-changing environment.


Power Words


  • gene: A segment of DNA that codes, or holds instructions, for a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
  • DNA: Short for deoxyribonucleic acid. DNA consists of four main components called nucleotides. These nucleotides are: A (adenine), T (thymine), C (cytosine), and G (guanine). As the nucleotides pair together in long chains, they form a double helix shape, which resembles a twisted ladder.
  • chromosome: A single piece of coiled DNA found in a cell's nucleus. A chromosome is generally X-shaped in animals and plants. Some segments of DNA in a chromosome are genes. Other segments of DNA in a chromosome are landing pads for proteins. The function of other segments of DNA in chromosomes is still not fully understood by scientists.


Source 3

Air pollution can mess with our DNA

Oosthoek, Sharon. Science News for Students (Jan 22, 2015).


  1. Air pollution can make it hard to breathe. It also can increase someone's blood pressure and heart rate. Those problems are well known. Now research suggests breathing diesel fumes can trigger another toxic change. It can inappropriately turn some genes on, while turning others off.
  2. A gene is a segment of DNA that tells cells of the body what to do -- and when. Genes can be controlled by a type of chemical switch, known as a methyl group (a carbon atom attached to three hydrogen atoms). Methyl groups cause a chemical reaction -- called methylation -- affecting a component of DNA. This tends to happen near a gene. Added methyl groups usually turn some gene off. The opposite tends to occur when you take a methyl group away, or demethylate a gene. Either change can alter health.
  3. And that can be a good thing. The body naturally produces methyl groups. This allows it to turn off genes when their action is no longer needed.
  4. But factors outside the body -- such as air pollutants -- may inappropriately step in and add methyl groups to DNA. Or they might remove methyl groups. These environmental changes can, in a sense, hijack genes, changing when or what they instruct cells to do.
  5. The study of methylation's role in gene action is called epigenetics (EH-pee- jen-EH- tiks). It describes changes that happen outside of your DNA. Indeed, these changes do not harm DNA. Instead, epigenetics may silence a gene (by inappropriately turning it off) or switch some gene on at the wrong time.
  6. And breathing diesel fumes for just two hours can have such an epigenetic effect, a new study finds. It was conducted by researchers at the University of British Columbia in Vancouver, Canada. They put 16 volunteers -- one at a time -- in an enclosed booth. It was about the size of a small bathroom. Each person remained there for two hours. Half breathed in clean air. The other half breathed air polluted with diesel fumes. Levels of that pollution were equal to what might occur in air along a highway in Beijing, China. Such levels also might occur at busy ports, rail yards, mines and industrial sites elsewhere in the world.
  7. To probe the effects of the pollution, the researchers looked at a volunteers' blood. They compared samples collected before the experiment to those taken 6 and 30 hours after someone had sat in the exposure booth. Methyl groups changed at about 2,800 different points on the DNA of people who breathed in diesel fumes. Those changes affected about 400 genes. No similar changes were seen among people breathing the clean air.
  8. At some DNA locations, exposure to diesel fumes added methyl groups. More often it reduced how many were present. That means a switch that normally would turn off a gene was more often flipped the other way. That could lead to unusually high gene activity.
  9. How these diesel-related changes might affect health is not yet clear, notes Ruiwei Jiang, an author of the new study. But the tests show that air pollution can alter DNA. The new data also suggest that diseases such as asthma might stem from prolonged episodes of methylation, Jiang says.
  10. "Even short-term exposure can cause these changes," she says. "So the question is: What are the cumulative effects for someone who breathes in diesel fumes regularly?" Jiang hopes other researchers will now try to answer this.
  11. Her team's findings were published December 9 in the journal Particle and Fibre Toxicology.
  12. Andrea Baccarelli studies environmental health and epigenetics at Harvard University in Boston, Mass. The new study is important because it shows that human DNA can be affected by short-term exposure to air pollution, he says. Until now, he says, scientists had largely thought that DNA "would respond primarily to long-term exposures."


Power Words


  • atom: The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and neutrally charged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
  • chemical: A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H 2 O.
  • diesel: Heavier and oilier than gasoline, diesel is another type of fuel made from crude oil. It's used to power many engines -- not only in cars and trucks but also to power some industrial motors -- that don't rely on spark plugs to ignite the fuel.
  • epigenetic changes: Molecular switches that can turn a gene on or off. Methyl groups -- chemical clusters each made of one carbon and three hydrogen atoms -- latch onto DNA near a gene. It's these methyl groups that can alter the programmed activity of a gene. Individuals can acquire an epigenetic change at any time during their lives.
  • molecule: An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O 2 ), but water is made of two hydrogen atoms and one oxygen atom (H 2 O).








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