Name Score. Better Living Through Genetics

Transcription

1 Name Score Better Living Through Genetics

2 Edible DNA Materials 2 Twizzlers 6 toothpicks 12 colored marshmallows (three of each color) Safety Concerns: Possible student allergy to foods being used, toothpicks. Ask students if they have an allergy to any of the foods being used. Discuss proper use of toothpicks. Procedures 1. Lay out your materials on your desk. 2. Using your Twizzlers, lay out the sides of the DNA molecule. 3. Assemble your marshmallow rungs. Remember, A only goes with T and C only goes with G. Make one color of marshmallow represent each base. Adenine Cytosine Guanine Thymine 4. Place one marshmallow on one end of your run and its partner on the other end. You should have 12 runs on your ladder when you are done. 5. Place each rung onto your licorice sides. Try and space them out evenly. You may place them in any order that you want. Make sure you do not have two of the same color marshmallows on one toothpick.

3 6. Twist your DNA molecule so that it looks like a double helix. 7. Identify the marshmallow bonds on your DNA molecule below: Chemical Adenine Marshmallow Color Cytosine Guanine Thymine 8. Once you are done, you must have your DNA graded. DNA model was completed correctly (Mr. Hill s initials) (used with Mr. Jones permission)

4 Color-Coded DNA Introduction Many people now get their DNA tested for hereditary diseases, including Huntington s Disease and some cancers. But soon, DNA may also be used to diagnose infectious diseases, from salmonella to HIV. In this Science Update, you ll hear about a developing technology that could make this possible. Article Seeking out DNA. I'm Bob Hirshon and this is Science Update. Most people associate DNA analysis with paternity tests and criminal investigations. But it can also be important for diagnosing illness. Bruce Armitage is a chemist at the Center for Light Microscope Imaging and Biotechnology. He s working on basic technology that could become a quick and easy way to screen for bacterial and viral DNA in the blood. He says it s based on a molecule called PNA and a group of special dyes. PNA is a labcreated version of DNA. It can be made so that it will seek out and connect to a specific DNA sequence. Armitage: By designing our PNA to have the right shape we can distinguish a viral DNA or a bacterial DNA from a human DNA. Armitage and his colleagues found that they can see if the PNA has found its target by adding special dyes to the mix. Armitage: What we ve found is that certain types of cyanine dyes will stick to a ladder where one of the strands is DNA, and one of the strands is PNA. And when they stick, they change color from blue to purple. Armitage says right now the test is only used in the research lab, but it could be improved for wider applications. For the American Association for the Advancement of Science, I'm Bob Hirshon.

5 Making Sense of the Research Bacterial and viral infections can be hard to spot. Often, a diagnosis is made based on symptoms. In the case of viral infections, even a firm diagnosis is done indirectly, by looking for antibodies that the body makes to fight the virus. This technique may make it possible to diagnose infections more quickly, efficiently, and confidently. The key player in the technology is PNA, an artificial version of DNA, the molecule that contains a living thing s genetic code. (PNA can also mimic RNA, a DNAlike molecule that viruses use instead.) PNA can be made to look like any specific strand of DNA or RNA. If it comes near a strand that matches, the PNA will stick to it. Since the genetic code of each organism is unique, it s possible to manufacture PNA strands that will stick to bacterial or viral DNA, but not to human DNA. Armitage says it s easier to do this with PNA than with actual DNA for two reasons: First, because you can synthesize as much PNA as you want, and make it exactly how you want it. Second, because PNA is more stable than DNA, it binds more firmly to its target and doesn t tend to come apart. Once the PNA binds to its target, the question is, how do you see it? That s where the dye, called cyanine, comes in. Cyanine dyes are the same light-absorbing dyes that are used in color photography. When PNA binds to DNA, the attached dye molecules end up stacking tightly on top of each other, and the apparent color changes from blue to purple. You can see this happen with the naked eye; all you need to do is put a couple of drops of cyanine dye in a small well where a DNA sample from the blood, for example is mixed with PNA. If it changes color, the bacteria or virus is present; if not, it isn t. Armitage says it isn t easy to make just the right strand of PNA. That s because the strands of DNA and RNA don t lie flat in living tissue: they re all tangled up like spaghetti. Sometimes a strand of PNA can t bind to its target, because the section of DNA it matches up with isn t exposed. So the researchers have to keep trying until they find a strand of PNA that works. Although the idea here is to diagnose infectious diseases, this isn t the only potential use for this technology. It could also be used to diagnose genetic diseases more easily. If scientists could manufacture a strand of PNA that matched up to a genetic sequence that causes a disease, they could turn it loose on a blood sample to see if the defective gene is there even if the patient doesn t have any symptoms yet.

6 1. What is PNA? How is it different from DNA or RNA? 2. How can it be used to spot bacterial or viral DNA? 3. Why are the cyanine dyes essential to this technique? 4. What are the advantages of this technique, compared with looking for the antibodies to a virus? Compared with diagnosing an illness based on the symptoms? 5. Some kinds of genetic testing for example, for incurable diseases have provoked controversy. Why do you think that is? Think of possible arguments for and against this kind of testing? Arguments For Arguments Against

7 Genes and Geography Introduction Our early human ancestors began migrating across the globe tens of thousands of years ago. Some left behind archaeological evidence of their travels. But as you'll hear in this Science Update, another record of where we come from and where we've been might be found right in our DNA. Article Genes and geography. I'm Bob Hirshon and this is Science Update. People around the world might look different from one another, but inside, we're pretty similar and that's true even of our genes. That's according to a recent study in the journal Science. Noah Rosenberg is a research associate at the University of Southern California. Using a computer program, he and his colleagues analyzed the genetic profiles of more than a thousand people from 52 places around the world. Rosenberg: One thing we found was that the amount of variation across populations was smaller than we had originally expected and smaller than had been found previously. So the vast majority of the sites in the genome are identical across all populations. Nevertheless, those sites could be used to predict that person's ancestry solely based on their DNA. That's because certain combinations of genetic types were more common in some regions than in others, and the computer program was powerful enough to tease those out. Rosenberg: This is helpful towards trying to figure out the relationships between different populations and the patterns of human migration. So combined with evidence from fields such as archaeology and linguistics, genetics can help scientists understand human history. For the American Association for the Advancement of Science, I'm Bob Hirshon.

8 Making Sense of the Research Although humans throughout history have made a really big deal over differences in populations, whether those differences are based on nationality, ethnicity, or skin color, the fact remains that we're all pretty similar. If you compare any two people to each other an Eskimo and a North African, a French woman and a Chinese man you'll find that 99.9% of their DNA is identical. In other words, everything that makes you unique is concentrated in less than one one-thousandth of your genes. What's more, even within that tiny fraction of DNA that varies between people, the differences between populations aren't as dramatic as the researchers expected. In fact, the overwhelming majority of genetic differences between individuals are just as variable within small populations as they are across the entire world. Comparatively speaking, only a small handful of genetic signatures are more common in some human populations than in others. Nevertheless, the researchers were able to use these tiny slivers of our genetic code to predict where people came from. They accomplished this by using a powerful computer program that analyzed hundreds of genetic signatures at once. By looking for patterns of "microsatellites" short strings of DNA that are passed down from generation to generation the researchers were able to make accurate statistical guesses about people's ancestries. So what good is this information? Well, for one thing, it could help out archaeologists and anthropologists who study the history of human migrations around the globe. But there's another, more practical use for it. For years, some doctors have been asking people about their ancestries in order to determine if they're genetically pre-disposed to certain diseases. But other doctors have argued that the question is useless because the idea of "ancestry" has no real genetic meaning. This study suggests that in some cases, where your ancestors came from may in fact have something to do with the kinds of genes you might be carrying. And that knowledge may not only help physicians assess an individual patient's risk for a disease, but also help epidemiologists (scientists who study diseases in populations) understand patterns of disease around the world.

9 1. About how similar are human beings genetically? 2. What is the difference between genes that simply vary from person to person, and genes that are distinctive of populations? Are distinctive genes shared by all members of a population? 3. What factors allowed the researchers to analyze such subtle variations in human genetics? 4. Can you think of specific situations in which this knowledge may be used? Give hypothetical examples for the following situations: A doctor-patient relationship An anthropologist studying the history of a population An epidemiologist studying a rare genetic illness

10 the punnett SquaRE practice PagE (from Luby s BioHelp, On this page is a set of "typical" genetics questions that are best answered using a Punnett square. Draw a Punnett Square and show your work! As always, do your best! P-squARe practice QueSTioN #1 Let's say that in seals, the gene for the length of the whiskers has two alleles. The dominant allele (W) codes long whiskers & the recessive allele (w) codes for short whiskers. a) What percentage of offspring would be expected to have short whiskers from the cross of two long-whiskered seals, one that is homozygous dominant and one that is heterozygous? b) If one parent seal is pure long-whiskered and the other is short-whiskered, what percent of offspring would have short whiskers?

11 P-squARE PraCTice question #2 In purple people eaters, one-horn is dominant and no horns is recessive. Draw a Punnett Square showing the cross of a purple people eater that is hybrid for horns with a purple people eater that does not have horns. Summarize the genotypes & phenotypes of the possible offspring. p-square practice QUestiON #3 A green-leafed luboplant (I made this plant up) is crossed with a luboplant with yellowstriped leaves. The cross produces 185 green-leafed luboplants. Summarize the genotypes & phenotypes of the offspring that would be produced by crossing two of the green-leafed luboplants obtained from the initial parent plants.

12 P-squARE PRacTice question #4 Mendel found that crossing wrinkle-seeded plants with pure round-seeded plants produced only round-seeded plants. What genotypic & phenotypic ratios can be expected from a cross of a wrinkle-seeded plant & a plant heterozygous for this trait (seed appearance)? Diagram of a Gene

13 Nectarines The origin of the fuzzless peach. I'm Bob Hirshon and this is Science Update. Today's Why Is It? question comes from Karen Hopkin Of Somerville, Massachusetts. She thought the nectarine was a cross between the peach and the plum. But she was startled to hear that the nectarine may actually be some sort of mutant peach. She wants to know what's what. Well, according to Wayne Sherman, a horticulturist at the University of Florida, the mutation theory wins out. Sherman: A nectarine is a mutation of peach from fuzzy skinned to no fuzzy skinned, or glaucoused from pubescence. That means peaches and nectarines essentially have the same genes. A peach tree will produce peaches if it inherits the dominant, fuzz-producing gene. But it'll make nectarines if it gets the recessive, or hairless, version of the gene. And Sherman says the gene does more than produce fuzz. Sherman: There are a number of factors that go along with the glaucous skin of the nectarine. Nectarines generally have more red color in the skin, more rounder shape, smaller size, more sugars, more acids, and more higher density. For the American Association for the Advancement of Science, I'm Bob Hirshon. Making Sense of the Research Although living things have thousands of genes, it's remarkable what a difference a single gene can make. In this case, the gene separates peaches from nectarines. As Sherman explains, it affects not only the skin of the fruit but also its color, shape, size, and flavor. This is a classic example of Mendelian genetics at work. Named after Gregor Mendel, the 19th-century monk who pioneered genetic science, it's a phrase that scientists use to describe the simplest patterns of genetic inheritance.

14 Nectarines and peaches demonstrate the pattern of simple dominance. Like people, animals, and most other living things, nectarine and peach trees have two copies of every gene one from each parent. (Yes, plants have parents.) The peach version is dominant and the nectarine version is recessive. In simple dominance, as long as one copy of the dominant gene is present, the dominant trait will be expressed (in other words, it will show up in the living thing). So if you have even one peach gene, you get a peach tree. You need two copies of the nectarine gene to get nectarines. There are other patterns of inheritance besides simple dominance. In incomplete dominance, if you have one copy of the dominant gene and one of the recessive, the living thing will be a hybrid that differs from both the pure dominant and pure recessive version. Many other traits are non-mendelian, which means that although they are inherited, they don't follow the simple patterns that Mendel first described. It's important to note that although nectarines are a mutant version of the peach, that doesn't mean they're "genetically engineered." Genetically-engineered foods are grown from plants whose genes were deliberately altered in the laboratory at some point in time. Nectarines are all-natural mutants that originated in China over 2,000 years ago.

15 1. What is a nectarine? 2. What does "simple dominance" mean? How does it relate to peaches and nectarines? 3. Which of the following would be possible, and why? Remember that each tree inherits one copy of the peach/nectarine gene from each parent. A) Cross two peach trees, get a peach tree (PP x PP or PP x Pp or Pp x Pp) B) Cross two peach trees, get a nectarine tree (Pp x Pp) C) Cross a peach and a nectarine tree, get a nectarine tree (PP x pp or Pp x pp) D) Cross a peach and a nectarine tree, get a peach tree (PP x pp or Pp x pp) E) Cross two nectarine trees, get a peach tree (pp x pp)

16 Genetics Practice Problems (from The Biology Corner Worksheets and Lessons) 1. For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho). AA Ee Ii Mm Bb ff Jj nn Cc Gg kk oo DD HH LL Pp 2. For each of the genotypes below determine what phenotypes would be possible. Purple flowers are dominant to white flowers PP Pp pp Round seeds are dominant to wrinkled seeds RR Rr rr Brown eyes are dominant to blue eyes BB Bb Bb Bobtails in cats are recessive TT Tt tt 3. For each phenotype below, list the genotypes (remember to use the letter of the dominant trait) Straight Hair is dominant to curly Straight Straight Curly Pointed heads are dominant to round heads Pointed Pointed Round

17 4. Set up the Punnet squares for each of the crosses listed below. Round seeds are dominant to wrinkled seeds. Rr x rr What percentage of the offspring will be round? RR x rr What percentage of the offspring will be round? RR x Rr What percentage of the offspring will be round? Rr x Rr What percentage of the offspring will be round? Practice with Crosses. Show all work! 5. A TT (tall) plant is crossed with a tt (short plant). What percentage of the offspring will be tall?

18 6. A Tt plant is crossed with a Tt plant. What percentage of the offspring will be short? 7. A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR). What percentage of the offspring will be homozygous (RR)? 8. A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant. What are the genotypes of the parents? x What percentage of the offspring will also be homozygous? 9. In pea plants purple flowers are dominant to white flowers. If two white flowered plants are cross, what percentage of their offspring will be white flowered?

19 10. A white flowered plant is crossed with a plant that is heterozygous for the trait. What percentage of the offspring will have purple flowers? 11. Two plants, both heterozygous for the gene that controls flower color are crossed. What percentage of their offspring will have purple flowers? What percentage will have white flowers? 12. In guinea pigs, the allele for short hair is dominant. What genotype would a heterozygous shorthaired guinea pig have? What genotype would a purebreeding shorthaired guinea pig have? What genotype would a longhaired guinea pig have?

20 13. Show the cross for a pure breeding shorthaired guinea pig and a longhaired guinea pig. What percentage of the offspring will have short hair? 14. Show the cross for two heterozygous guinea pigs. What percentage of the offspring will have short hair? What percentage of the offspring will have long hair? 15. Two shorthaired guinea pigs are mated several times. Out of 100 offspring, 25 of them have long hair. What are the probable genotypes of the parents? x Show the cross to prove it!

21 Genetics With a Smile (modified from a lesson by T. Trimpe, Part A: Smiley Face Traits Obtain two coins from your teacher. Mark one coin with an F and the other with an M to represent each of the parents. The parents are heterozygous for all the Smiley Face traits. Flip the coins for parent for each trait. If the coin lands with heads up, it represents a dominant allele. A coin that lands tails up indicates a recessive allele. Record the result for each person by circling the correct letter. Use the results and the Smiley Face Traits page to determine the genotype and phenotype for each trait. Trait Female Male Genotype Phenotype Face Shape C c C c Eye Shape E e E e Hair Style S s S s Smile T t T t Ear Style V v V v Nose Color D d D d Face Color Y y Y y Eye Color B b B b Hair Length L l L l Freckles F f F f Nose Color R Y R Y Ear Color P T P T Part B: Is it a boy or girl? To determine the sex of your smiley face, flip the coin for the male parent. Heads would represent X, while tails would be Y.

22 Female Male Genotype Phenotype Sex X X Y Part C: Create Your Smiley Face! Use the Smiley Face Traits chart and your results from Part A to create a sketch of your smiley face in the box. Do this on a separate sheet of paper. Once you have completed the sketch, use the drawing tools in Microsoft Word to create your smiley face! Also, remember... Don t forget to give your smiley face a name! You will also need to include your name as parent and your class.

23 Our Baby Parents

24 Genetics with a Smile Wrapping It Up! 1. How does your smiley face compare to the ones created by your classmates? Pick two different parents and compare each of the 12 traits. Indicate the phenotype for each smiley face for each trait in the chart. Trait Our Smiley Face Smiley Face by: Smiley Face by: Face Shape Eye Shape Hair Style Smile Ear Style Nose Color Face Color Eye Color Hair Length Freckles Nose Color Ear Color 2. Which smiley face has the most dominant traits? How many? traits? 3. Which smiley face has the most recessive traits? How many? traits?

25 4. What is the probability that a smiley face will have a green face? out of or % 5. How many smiley faces have a green face, which is a recessive trait? out of or % 6. How does your predicted probability for a green face (#5) compare to the actual results (#6)? Explain. 7. What is the probability that a smiley face will have an orange nose? out of or % 8. How many smiley faces have an orange nose? out of or % 9. Why did you only need to flip the male parent coin to determine the sex of your smiley face? 10. Uncle Smiley, who is heterozygous for a yellow face, married a woman with a green face. Both of them have always wanted a large family! If they were to have 12 children, what is the probability that the children would have yellow faces? How many would have green faces? Create a Punnett square to help you find your answers. 11. Grandma and Grandpa Smiley are heterozygous for the star eye shape. If one of their heterozygous children married a girl with blast-type eyes, what percentage of their grandchildren should have starry eyes? What percent would have blast-type eyes? Create a Punnett square to help you find your answers.

26 12. Baby Smiley has curly hair, but neither of her parents do! Is this possible? Create a Punnett square to help you find your answer. Bikini Bottom Genetics (from a worksheet by T. Trimpe Scientists at Bikini Bottoms have been investigating the genetic makeup of the organisms in this community. Use the information provided and your knowledge of genetics to answer each question. 1. For each genotype below, indicate whether it is a heterozygous (He) OR homozygous (Ho). TT Bb DD Ff tt dd Dd ff Tt bb BB FF 2. Determine the phenotype for each genotype using the information provided about SpongeBob. Yellow body color is dominant to blue. YY yy Yy Square shape is dominant to round. SS ss Ss

27 3. For each phenotype, give the genotypes that are possible for Patrick. A tall head (T) is dominant to short (t). Tall = Pink body color (P) is dominant to yellow (p). Pink body = Short = Yellow body = 4. SpongeBob SquarePants recently met SpongeSusie Roundpants at a dance. SpongeBob is heterozygous for his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities that would result if SpongeBob and SpongeSusie had children. HINT: Read question #2! A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with a square shape? out of or % C. What are the chances of a child with a round shape? out of or % 5. Patrick met Patti at the dance. Both of them are heterozygous for their pink body color, which is dominant over a yellow body color. Create a Punnett square to show the possibilities that would result if Patrick and Patti had children. HINT: Read question #3! A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with a pink body? out of or % C. What are the chances of a child with a yellow body? out of or %

28 6. Everyone in Squidward s family has light blue skin, which is the dominant trait for body color in his hometown of Squid Valley. His family brags that they are a purebred line. He recently married a nice girl who has light green skin, which is a recessive trait. Create a Punnett square to show the possibilities that would result if Squidward and his new bride had children. Use B to represent the dominant gene and b to represent the recessive gene. A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with light blue skin? % C. What are the chances of a child with light green skin? % 7. Assume that one of Squidward s sons, who is heterozygous for the light blue body color, married a girl that was also heterozygous. Create a Punnett square to show the possibilities that would result if they had children. A. List the possible genotypes and phenotypes for their children. B. What are the chances of a child with light blue skin? % C. What are the chances of a child with light green skin? % 8. Mr. Krabbs and his wife recently had a Lil Krabby, but it has not been a happy occasion for them. Mrs. Krabbs has been upset since she first saw her new baby who had short eyeballs. She claims that the hospital goofed and mixed up her baby with someone else s baby. Mr. Krabbs is homozygous for his tall eyeballs, while his wife is heterozygous for her tall eyeballs. Some members of her family have short eyes, which is the recessive trait. Create a Punnett square using T for the dominant gene and t for the recessive one.

29 A. List the possible genotypes and phenotypes for their children. B. Did the hospital make a mistake? Explain your answer. Oompah Loompa Genetics 1. Oompahs generally have blue faces which is caused by a dominant gene. The recessive condition results in an orange face. Develop a "key" to show the genotypes and phenotypes possible for Oompa Loompas. 2. Two heterozygous Oompahs are crossed. What proportion of the offspring will have orange faces? 3. A blue-faced Oompah (homozygous) is married to an orange-faced Oompah. They have eight children. How many children will have blue faces?

30 4. Otis Oompah has an orange face and is married to Ona Oompah who has a blue face. They have 60 children, 31 of them have orange faces. What are the genotypes of the parents? 5. Odie Oompah has a blue face. In fact, everyone in Odie's family has a blue face, and the family boasts that it is a "pure" line. Much to his family's horror, he married Ondi Oompah who "gasp" has an orange face. What are the genotypes of their children? Is Odie's line still "pure"? 6. Ona Oompah (from#4) divorces Otis and marries Otto. Otto has an orange face. What is the probability that Ona and Otto's children will have orange faces? 7. Oompahs can have red, blue or purple hair. Purple hair results from the heterozygous condition. Make a "key" showing the genotypes and phenotypes for hair color. Is this an example of codominance or incomplete dominance?

31 8. Orville Oompah has purple hair and is married to Opal Oompah who brags that she has the bluest hair in the valley. How many of Opal's children will be able to brag about their blue hair also? 9. Olga Oompah has red hair and marries Oliver Oompah who has blue hair. They have 32 children. What color is their children's hair? 10. Olivia Oompah is married to Odo Oompah and they both have purple hair. What color hair and in what proportion would you expect their children to have? 12. In the land of Oompah, blue hair is highly valued, blue haired Oompahs even get special benefits. Oscar Oompah has purple hair but he wants to find a wife that will give him blue haired children. What color hair should his wife have? What would be his second choice?