Traits and Heredity. Teacher's Guide. Visual Learning Company Editors: Brian A. Jerome Ph.D. Stephanie Zak Jerome

Transcription

1 Traits and Heredity Teacher's Guide Editors: Brian A. Jerome Ph.D. Stephanie Zak Jerome Assistant Editors: Louise Marrier Hannah Fjeld Graphics: Fred Thodal Heidi Berry Brian Bliven Emily Merkert Lyndsey Canfield Union Street Brandon VT 05733

2 A Message from our Company... Visual Learning is a Vermont-based, family owned company specializing in the creation of science programs. As former classroom science teachers we have designed our programs to meet the needs and interests of both students and teachers. Our mission is to help educators and students meet educational goals while experiencing the thrill of science! Viewing Clearances The video and accompanying teacher s guide are for instructional use only. In showing these programs, no admission charges are to be incurred. The programs are to be utilized in face-to-face classroom instructional settings, library settings, or similar instructional settings. Duplication Rights are available, but must be negotiated with the Visual Learning Company. Television, cable, or satellite rights are also available, but must be negotiated with the. Closed circuit rights are available, and are defi ned as the use of the program beyond a single classroom but within a single campus. Institutions wishing to utilize the program in multiple campuses must purchase the multiple campus version of the program, available at a slightly higher fee. Discounts may be granted to institutions interested in purchasing programs in large quantities. These discounts may be negotiated with the. Use and Copyright: The purchase of this video program entitles the user the right to reproduce or duplicate, in whole or in part, this teacher s guide and the black line master handouts for the purpose of teaching in conjunction with this video,. The right is restricted only for use with this video program. Any reproduction or duplication, in whole or in part, of this guide and student masters for any purpose other than for use with this video program is prohibited. The video and this teacher s guide are the exclusive property of the copyright holder. Copying, transmitting, or reproducing in any form, or by any means, without prior written permission from the copyright holder is prohibited (Title 17, U.S. Code Sections 501 and 506). Copyright 2006 ISBN

3 Table of Contents A Message from our Company Viewing Clearances Use and Copyright National Standards Correlations Student Learning Objectives Assessment Introducing the Program Program Viewing Suggestions Video Script Answer Key to Student Assessments Answer Key to Student Activities Pre-Test Post-Test Video Review Vocabulary Writing Activity Dominant and Recessive Traits Acquired vs Inherited Traits Genetic Engineering The Double Helix

4 National Standards Correlations Benchmarks for Science Literacy (Project AAAS) The Living Environment - Heredity (5B) Grades 3-5 By the end of the fi fth grade, students should know that: Some likenesses between children and parents, such as eye color in human beings, or fruit or flower color in plants, are inherited. Other likenesses, such as people s table manners or carpentry skills, are learned. For offspring to resemble their parents, there must be a reliable way to transfer information from one generation to the next. National Science Education Standards (Content Standards: K-4, National Academy of Sciences) Life Science - Content Standard C: Many characteristics of an organism are inherited from the parents of the organism, but other characteristics result from an individual s interactions with the environment. Inherited characteristics include the color of fl owers and the number of limbs of an animal. Other features, such as the ability to ride a bicycle, are learned through interactions with the environment and cannot be passed on to the next generation

5 Student Learning Objectives Upon viewing the video and completing the enclosed student activities, students will be able to do the following: Defi ne traits as the distinguishing characteristics of an organism. Describe heredity as the process of passing on traits from parents to offspring. Differentiate between acquired traits and inherited traits, giving examples of each. Identify Gregor Mendel as the father of modern genetics, and defi ne genetics as the study of heredity. Briefl y describe Mendel s Law of Dominance, explaining that the stronger trait is called the dominant trait and the weaker trait is the recessive trait. Generally explain that chromosomes are structures in cells that contain genetic material. Defi ne DNA as the chemical that determines the genetic code. Understand that genetic engineering is a fi eld of scientifi c research that has accomplished many benefi cial things. However, also understand that there is some controversy and concern about the longterm effects of genetic engineering

6 Assessment Preliminary Test (p ): The Preliminary Test is an assessment tool designed to gain an understanding of students preexisting knowledge. It can also be used as a benchmark upon which to assess student progress based on the objectives stated on the previous pages. Post-Test (p ): The Post-Test can be utilized as an assessment tool following student completion of the program and student activities. The results of the Post-Test can be compared against the results of the Preliminary Test to assess student progress. Video Review (p. 18): The Video Review can be used as an assessment tool or as a student activity. There are two sections. The fi rst part contains questions displayed during the program. The second part consists of a fi ve-question video quiz to be answered at the end of the video

7 Introducing the Program Before showing the video program to students, ask students to feel their earlobes. Also tell them to look closely at the earlobes of some of their classmates. Explain that there are two different types of earlobes: attached and unattached. Have students observe a classmate who has attached earlobes and one who has unattached earlobes. Next ask students if they can play a musical instrument. Again have them compare the results with the entire class. Next tell students that these sorts of distinguishing characteristics can also be called traits. Write the word trait on the board. Ask students if they can think of any other traits. Make two lists of different traits on the board, separating inherited and acquired traits. Ask students if they notice a difference between the two lists. Introduce the concept of acquired traits which are skills that you learn. Discuss the concept of inherited traits, which are traits you inherit from your parents. Tell students to pay close attention to the video to learn more about traits and heredity. Program Viewing Suggestions The student master Video Review is provided (p. 18) for distribution to students. You may choose to have your students complete this Master while viewing the program or do so upon its conclusion. The program is approximately 14 minutes in length and includes a fi ve-question video quiz. Answers are not provided to the Video Quiz in the video, but are included in this guide on page 12. You may choose to grade student quizzes as an assessment tool or to review the answers in class. The video is content-rich with numerous vocabulary words. For this reason you may want to periodically stop the video to review and discuss new terminology and concepts

8 Video Script 1. Has anyone ever told you that you have your mother s or your father s eyes? 2. Or have you ever wondered why the children in a certain family all look so similar? 3. These similarities not only occur in people but in plants and animals as well. 4. Perhaps you have looked at fl owers in a garden and been amazed at how they all look very alike. 5. Notice how this calf looks so similar to its mother. 6. What causes these similarities between offspring and parents? 7. Or why in some cases do parents and offspring look different from each other? 8. During the next few minutes we are going to explore these questions as we take a look at some of the factors involved in passing characteristics from parents to offspring. 9. And we will discuss some of the major scientifi c discoveries which have given us a greater understanding of traits and heredity. 10. Graphic Transition What is Heredity? 11. Things such as the color of your hair, the color of your eyes, the markings on the wings of a butterfl y, and the shape of this bird s beak are all characteristics. 15. Another word for characteristics is traits. 16. We have thousands of different traits. 17.Some of these traits, such as skin color and the shape of our ears are traits we can easily observe. 18.Other traits, such as the shape of a heart valve, or blood type are more diffi cult to see. 19.A living thing, whether it be a person, animal, or plant has many different traits. 21.Some traits, such as hair color, are passed on from parents to offspring, while others such as athletic ability are not. 22. Heredity is the process of passing on traits from parents to offspring. 23.Let s take a minute to compare traits that are passed on and those that are not. 24. Graphic Transition Acquired and Inherited Traits 25.Think about a skill you had to develop, such as reading playing soccer or playing a musical instrument. 28. You Decide! Are these skills inherited or learned? 29.That s right, these skills are learned. You are not born with these traits but over time, and with practice, you acquired these skills. Things that you learn are called acquired traits. 30.Some traits such as hair color, eye color, or your height are not acquired. You can t learn or practice something to make your eyes blue. 31. These types of traits are called inherited traits. 32. Inherited traits are characteristics that you are born with. 33.Let s now take a closer look at inherited traits

9 Video Script 34. Graphic Transition Inherited Traits 35.Our understanding of the process of heredity is relatively young, and we are learning new things all the time. 36.It was not until the 1860 s that the fi eld of genetics began to take form. 37. Genetics is the study of the process of heredity. 38.In the 1860 s an Austrian monk by the name of Gregor Mendel performed thousands of experiments that established the foundation of the science of genetics. 39. Working mainly with pea plants in his garden, Mendel studied a number of different traits such as pea plant height, seed color, seed shape and fl ower position to name just a few. 42.He became very interested in the way these traits were passed on from parents to offspring over several generations. 43.Mendel himself was also able to control the appearance of traits in offspring by directly controlling the breeding process. 44.Over a period of seven years, Gregor Mendel took careful notes on the 20,000 plants that he grew. 45.From his work, Mendel hypothesized that two factors exist for a given characteristic. 46.For example, in the trait for plant height, one factor for height comes from the father, and the other factor for height comes from the mother. 47. Today scientists call the factors that control traits genes. 48. Genes are the basic units of heredity. 49. Let s explore how genes can interact with each other. 50. Graphic Transition Dominant and Recessive Traits 51.One of Mendel s most important discoveries dealt with the principle of dominance and recessiveness. 52.He reasoned that in some cases one factor could mask another factor. 53.For example, in the case of pea plant height, the trait of tall height masks, or dominates, the factor for short plant height. 54. The stronger trait which masks the weaker trait is called the dominant trait. 55. And the weaker trait that seemed to disappear is called the recessive trait. 56.This principle is summarized in the Law of Dominance, which states that in a living thing the dominant trait is expressed and the recessive trait is hidden. 57.There are many traits in humans which are dominant and recessive including earlobe formation, hairline appearance, 58...and even the ability to roll your tongue. 59.The idea of dominance and recessiveness is just one of the many important discoveries Gregor Mendel made while working with pea plants in his garden. 60. Graphic Transition Chromosomes 61.The work of Gregor Mendel went largely unnoticed for over 30 years. 62.But in the early 1900 s scientists rediscovered his work, which serves as the foundation for the modern science of genetics. 63. Scientists agreed with Mendel s earlier fi ndings that certain traits are inherited from parents. 64.And they also discovered that genes responsible for traits, are found inside cells on small

10 Video Script structures called chromosomes. 65. Chromosomes contain genetic material made up of many, many genes. 66. Every cell in the body contains chromosomes. 67.Today we know that chromosomes, magnifi ed here many hundreds of times, control the traits of an organism. 68. Graphic Transition DNA 69. In the 1940 s and 1950 s several scientists including Martha Chase, Alfred Hershey, Edwin Chargaff, Rosalind Franklin, and Maurice Wilkins as well as James Watson and Francis Crick added to our understanding of genetic material. 71.They found that the genetic material, which makes up genes, consits of a complex chemical called deoxyribonucleic acid, or DNA for short. 72. You Observe! Describe the shape of this DNA molecule. 73.That s right, the DNA molecule kind of looks like a ladder that has been twisted. 74.Scientists call the shape of the DNA molecule a double helix. 75.A close inspection shows that the rungs on the double helix are formed by pairs of substances called nitrogen bases The DNA ladder may contain hundreds of millions of pairs of nitrogen bases. 76.There are four different types of nitrogen bases in DNA. These bases combine in specifi c ways. 77. The arrangement of the bases determines the genetic code. 78. Graphic Transition Genetic Engineering 79.One of the most active fi elds of scientifi c investigation involves studying the genetic code not only of humans, but of all kinds of living things from plants to animals to viruses. 81.Genetic engineering involves the amazing process of actually changing the genetic makeup of a living thing. 82.For example, scientists have produced vaccines by genetically changing viruses to protect us from harmful diseases. 83.Genetic engineering has also created crops which are more resistant to disease, and also produce higher yields. 84.Through genetic engineering, microorganisms have even been altered to process sewage and even clean up oil spills. 85. While there have been numerous benefi ts from genetic engineering there is concern about the long-term effects that genetically altered organisms may have on people and the environment. 87. Graphic Transition Summing Up 88.During the past few minutes we have briefl y explored some of the aspects of traits and heredity. 89. We began by discussing how traits are characteristics of an organism. 90.We observed that some traits, such as eye color, are inherited traits, while others such as playing an instrument are acquired traits. 91.Heredity is the study of the passing of traits from parents to offspring

11 Video Script 92. Some of the early work of Gregor Mendel was highlighted, particularly the concept of dominant and recessive traits. 94. We saw that the genetic material is found on chromosomes inside cells. 95. The actual material which makes up the genetic code-dna was also described. 96. Finally, we discussed some of the benefi ts and concerns of genetic engineering. 97.So the next time you look in the mirror or spend time with family members Think about some of the things we have discussed during the past few minutes You just might think about traits and heredity a little differently Graphic Transition Video Assessment 102. Fill in the correct word to complete the sentence. Good luck and let s get started! 1. are the characteristics of a living thing. 2. Hair color is an example of an trait. 3. is the study of heredity. 4. are made up of many, many genes. 5. is the genetic material found in genes. Answers can be found on page

12 Answer Key to Student Assessments Pre-Test (p ) 1. c - traits 2. a - heredity 3. d - acquired trait 4. b - inherited trait 5. a - genetics 6. b - pea plants 7. c - dominant 8. d - recessive 9. c - DNA 10. a - genetic engineering 11. true 12. false 13. false 14. true 15. false 16. Heredity is the process of passing on traits from parents to offspring. 17. An example of an acquired trait is the ability to play the piano. An example of an inherited trait is the color of your eyes. 18. Genetics is the study of heredity. 19. When you say a trait is dominant, it means that the stronger trait sometimes masks the weaker trait. 20. DNA is the complex chemical compound that makes up genetic material. Post-Test (p ) 1. c - dominant 2. b - inherited trait 3. c - DNA 4. d - recessive 5. d - acquired trait 6. c - traits 7. a - genetics 8. a - genetic engineering 9. a - heredity 10. b - pea plants 11. false 12. false 13. true 14. true 15. false 16. DNA is the complex chemical compound that makes up genetic material. 17. When you say a trait is dominant, it means that the stronger trait sometimes masks the weaker trait. 18. Heredity is the process of passing on traits from parents to offspring. 19. Genetics is the study of heredity. 20. An example of an acquired trait is the ability to play the piano. An example of an inherited trait is the color of your eyes. Video Review (p. 18) 1. The skills, such as reading, playing soccer, or playing a musical instrument, are learned skills. 2. The DNA molecule looks like a ladder that has been twisted. The shape is called a double helix. 1. traits 2. inherited 3. Genetics 4. Chromosomes 5. DNA

13 Answer Key to Student Activities Vocabulary (p. 19 ) 1. heredity 2. acquired 3. traits 4. chromosomes 5. genetic engineering 6. dominant 7. inherited 8. DNA 9. recessive 10. genetics Writing Activity (p. 20) Characteristics of an organism are called traits. The process of passing traits from parents to offspring is known as heredity. Not all traits are passed on by parents to offspring. Skills that you must practice to learn are called acquired traits. The study of heredity is genetics. Gregor Mendel was one of the fi rst scientists to study genetics. Mendel developed the Law of Dominance. It states that stronger traits often mask weaker traits. The weaker traits are called recessive traits. In the 1950s, scientists discovered DNA, the chemical that makes up genes. Genes are responsible for the traits of an organism. Through the process of genetic engineering scientists have been able to alter the genetic makeup of a living thing. In Your Own Words (p. 20) 1. Heredity is the name for the way that traits are passed from one generation to the next. 2. An inherited trait is a trait that is passed on from the parents to offspring. An acquired trait is a trait that is learned or obtained over time. 3. The role of DNA is to hold the genetic material of an organism. Dominant and Recessive Traits (p ) 1. In his experiments with pea plants, Gregor Mendel controlled the breeding of the parents in order to see exactly how traits were passed from one generation to the next. 2. Mendel discovered dominant traits and recessive traits. Dominant traits are the stronger traits that usually mask the weaker recessive traits. 3. From his mother, the child inherited curly hair, unattached earlobes, and dimples. Dominant and Recessive Traits cont d. 4. The offspring inherited a widow s peak and cleft chin from his father. 5. Recessive traits that can be seen in the pictures are straight hair, straight hairline, attached earlobes, no dimples, and smooth chin. 6. You can assume which traits are recessive because they are the traits that do not appear in the offspring. Acquired vs. Inherited Traits (p. 23) Height Using a computer Eyecolor Shoe size Driving a car Skin color Reading Playing the guitar Hitting a baseball Blood type Shape of your nose Speaking French Pierced ears Freckles inherited acquired inherited inherited acquired inherited acquired acquired acquired inherited inherited acquired acquired inherited Genetic Engineering (p. 24) 1. Genetic engineering is the process that allows scientists to change the genetic makeup of a living thing. 2. A GMO is a genetically modifi ed organism, the fi rst GMO was created in Benefi ts of genetic engineering include creating foods that are resistant to disease, and developing medecines. Concerns are that the environment will become less diverse, and that the long term effects are completely unknown. The Double Helix (p.25) 1. The structure of DNA was discovered in 1953 by James D. Watson and Francis Crick. 2. The double helix looks like a ladder that has been twisted. 3. There are four different types of nitrogen bases in DNA. The arrangement of the bases determines the genetic code

14 Pre-Test Name Circle the best answer for each of the following questions. 1. Another word for characteristics of a living thing is: a. markings b. flowers c. traits d. tasks 2. The process of passing on traits from parents to offspring is called: a. heredity b. ability c. skills d. reproduction 3. A trait that you learn is an: a. applied trait b. inherited trait c. hard trait d. acquired trait 4. If you get a trait from your parents, it is referred to as an (a): a. simple trait b. inherited trait c. easy trait d. acquired trait 5. What is the science of heredity called? a. genetics b. paleontology c. biology d. chemistry 6. Gergor Mendel worked with this organism in his studies of heredity: a. mice b. pea plants c. rats d. moss 7. The stronger trait which tends to mask a weaker trait is called: a. winning b. recessive c. dominant 8. A weak trait that seemingly disappears is referred to as: a. fading b. dominant c. losing d. powerful d. recessive 9. What substance determines genetic code? a. blood b. marrow c. DNA d. acid 10. The process of altering the genetic make-up of a living thing is: a. genetic engineering b. biochemistry c. physics d. paleontology 14

15 Pre-Test Name Write true or false next to each statement Hair color is an example of an inherited trait. If you practice and study enough, you can make your eyes blue. Gregor Mendel bred horses to study genetics. Chromosomes contain the genetic material found in cells. Genetic engineering has been unsucessful in changing the genes of living things. Write a short answer for each of the following. 16. What is heredity? 17. List one example each of an acquired trait and an inherited trait. 18. What is genetics? 19. What does it mean to say a trait is dominant? 20. What is DNA? 15

16 Post-Test Name Circle the best answer for each of the following questions. 1. The stronger trait which tends to mask a weaker trait is called: a. winning b. recessive c. dominant d. powerful 2. If you get a trait from your parents, it is referred to as an (a): a. simple trait b. inherited trait c. easy trait d. acquired trait 3. What substance determines genetic code? a. blood b. marrow c. DNA 4. A weak trait that seemingly disappears is referred to as: a. fading b. dominant c. losing d. acid d. recessive 5. A trait that you learn is an: a. applied trait b. inherited trait c. hard trait d. acquired trait 6. Another word for characteristics of a living thing is: a. markings b. flowers c. traits d. tasks 7. What is the science of heredity called? a. genetics b. paleontology c. biology d. chemistry 8. The process of altering the genetic make-up of a living thing is: a. genetic engineering b. biochemistry c. physics d. paleontology 9. The process of passing on traits from parents to offspring is called: a. heredity b. ability c. skills d. reproduction 10. Gergor Mendel worked with this organism in his studies of heredity: a. mice b. pea plants c. rats d. moss 16

17 Post-Test Name Write true or false next to each statement If you practice and study enough, you can make your eyes blue. Genetic engineering has been unsucessful in changing the genes of living things. Chromosomes contain the genetic material found in cells. Hair color is an example of an inherited trait. Gregor Mendel bred horses to study genetics. Write a short answer for each of the following. 16. What is DNA? 17. What does it mean to say a trait is dominant? 18. What is heredity? 19. What is genetics? 20. List one example each of an acquired trait and an inherited trait. 17

18 Video Review Name While you watch the video, answer these questions: You Decide! 1. Are these skills inherited or learned? You Observe! 2. Describe the shape of this DNA molecule. After you watch the video, test your knowledge with these questions. 1. are the characteristics of a living thing. 2. Hair color is an example of an trait. 3. is the study of heredity. 4. are made up of many, many genes. 5. is the genetic material found in genes. 18

19 Vocabulary Name Use these words to fill in the blanks next to the sentences below. Words DNA genetics inherited heredity recessive dominant acquired chromosomes traits genetic engineering The process of passing traits from parents to offspring. Traits that are learned or developed over time Another word for characteristics of an organism. Small structures in cells that contain genetic material The process of changing the genetic makeup of an organism. The stronger trait that sometimes masks the weaker characteristic. Traits that you are born with The chemical that makes up genetic material. The weaker trait that seemingly disappears. 10. The study of the process of heredity. 19

20 Writing Activity Name W genetics DNA heredity Dominance traits acquired recessive engineering Use the correct word from above to complete the sentences in the following paragraph. Characteristics of an organism are called. The process of passing traits from parents to offspring is known as. Not all traits are passed on by parents to offspring. Skills that you must practice to learn are called traits. The study of heredity is. Gregor Mendel was one of the fi rst scientists to study genetics. Mendel developed the Law of. It states that stronger traits often mask weaker traits. The weaker traits are called traits. In the 1950s, scientists discovered, the chemical that makes up genes. Genes are responsible for the traits of an organism. Through the process of genetic scientists have been able to alter the genetic makeup of a living thing. In Your Own Words 1. What is heredity? 2. What is an inherited trait? What is an acquired trait? 3. What is the role of DNA? 20

21 Dominant and Recessive Traits Name Background: Gregor Mendel, an Austrian monk, is often credited with beginning the science of genetics in the 1860s. By controlling the breeding of pea plants, Mendel was able to see exactly how traits were passed down from one generation to the next. Through his careful experiments with over 15,000 pea plants Mendel learned a great deal about the process of heredity. One of Gregor Mendel s most important discoveries was the difference between dominant and recessive traits. Mendel developed a principle called the Law of Dominance. It states that there are two different forms of a trait. The dominant trait is the stronger trait, which is usually expressed in the offspring. The recessive trait is the weaker trait; it is not usually visible in the offspring. For example, in the case of pea plant height, the trait for tallness dominates that of shortness. In pea plants, tallness is a dominant trait. People have dominant and recessive traits as well. For example, feel your earlobes. Are they attached directly to your head? Or do they hang free? In the case of earlobes, unattached earlobes are dominant over attached earlobes. Directions: Look carefully at the pictures of the parents and offspring below. Decide which traits you think are inherited from the mother and which traits are inherited from the father. Finally, answer the questions on the next page. Mother Father curly hair straight hair straight hairline widow s peak unattached earlobes attached earlobes dimples no dimples smooth chin cleft chin curly hair Offspring widow s peak unattached earlobes dimples cleft chin 21

22 Dominant and Recessive Traits Name Questions: 1. What did Gregor Mendel control in his experiments with pea plants? Why did he do this? 2. List the two types of traits that Mendel discovered, and describe them. 3. Which traits did the child get from his mother? 4. Which traits did he get from his father? 5. List all of the recessive traits you noticed in the pictures. 6. How did you know which traits were recessive? 22

23 Acquired vs. Inherited Traits Name Background: You probably already know that the characteristics of an organism are referred to as traits. There are two different kinds of traits, characteristics you are born with, and those that you learn or obtain over time. Traits that you have from birth are called inherited traits. For example, the color of your hair is an inherited trait. Those traits that you must learn or develop during your life, such as playing the violin, are acquired traits. In this activity you will practice distinguishing between inherited traits and acquired traits. Directions: For each of the traits listed below, decide whether the trait is acquired or inherited. Height Using a computer Eyecolor Shoe size Driving a car Skin color Reading Playing the guitar Hitting a baseball Blood type Shape of your nose Speaking French Pierced ears Freckles 23

24 Genetic Engineering People have controlled the reproduction of some animals and plants for many years. Today, scientists are using techniques that allow them to change the genetic makeup of a living thing. This process is called genetic engineering. It is one of the most active fi elds of scientifi c research today. Using genetic engineering, scientists are able to change an organism s genetic code. This means that they can create plants and animals with desirable traits without breeding. The organisms that result from genetic engineering are called genetically modifi ed organisms, or GMOs. The fi rst GMO was created in Since then, scientists have created many different types of genetically modifi ed organisms. For example, scientists have cloned the genetic code of a sheep. This means that there are two sheep that have the exact same genetic code. Scientists have also used genetic engineering to create a type of corn that repels insects. Some people believe that genetically modifi ed foods will be able to save people who are starving. This would happen because foods like the corn can grow in harsh conditions and provide more nutrients. Insulin is a chemical that people with diabetes need. Scientists can produce insulin using genetic engineering. However, not everyone believes that genetic engineering is a good thing. Some people say that it is not a good idea to change the natural makeup of a living thing. Others argue that GMOs will make the environment less diverse because GMOs are stronger than natural plants and animals. The long term effects of GMOs are completely unknown. There are both benefi ts and concerns about genetic engineering. Questions: 1. What is genetic engineering? Name Read the information below, and then answer the questions. 2. What is a GMO and when was the fi rst one created? 3. What are some benefi ts of genetic engineering? What are some concerns? 24

25 The Double Helix Name Background: In 1953, two scientists, James D. Watson and Francis Crick, discovered the structure of DNA. They found the shape of the DNA molecule to be a double helix, as pictured to the right. The double helix looks like a ladder that has been twisted. Each of the rungs on the ladder is made up of a pair of nitrogen bases. There are four different types of nitrogen bases in DNA. The sequence of these chemicals creates the unique genetic code of every organism. Today we know that the nitrogen bases always pair up in the following confi guations: cytosine - guanine, adenine - thymine. Directions: Using four colors, color in the double helix at the right side of this page. Pay close attention to the pairs of nitrogen bases as you color. Use one color to signify each of the four types of nitrogen bases. Then answer the questions below. Questions: 1. When was the structure of DNA discovered, and by who? 2. Describe the appearance of a double helix. 3. How many different types of nitrogen bases are in DNA? What does the arrangement of these bases determine? 25