Genetics

Online Lesson Plan
Genetics

lrKathyThrough the following investigations, students will become familiar with the basic concepts of inheritance. Most 5th-8th graders can understand cells contain structures carrying the genetic materials. They can also grasp the concept each parent contributes one half of the genetic material for each offspring.

Lesson Plan by Kathy Jacobitz, science education consultant, Pawnee City, Nebraska.

Objectives

Suggested grade level – 5th-8th.

standards02

  • The student will use the scientific inquiry for the investigations.
  • The student will be able to perform simple genetic crosses in the study of genetics.
  • The student will prove which traits are dominant and recessive.
  • A geneticist produces hybrids for farmers. The student will be able to state the role of genetics in agriculture.
  • The student will explore the history of genetics.

 

Introduction

crops0201Perform a KWL – What We Know / What We Want to Know / What we Learned – about genetics and hybrids for each student and combine the ideas for a class KWL. All information needs to be recorded in the student journal.

Practice the journal activity with corn and move on to your genetics study using fruit flies followed by fast grow plants. From the journal activity students should start observing differences within a given type of organism.

Students will be asked to develop an experiment with hybrids produced in the first generation, F1, using fruit flies and/or plants. The study will allow the students to learn the meaning of genotype and phenotype, recessive and dominant traits while performing and interpreting a Punnett square.

Resources

  1. Story pages on this Web site including Hybrid Crops
  2. The Science of Hybrids
  3. Henry A. Wallace
  4. Henry Beachel
  5. Livestock
  6. Selective Breeding
  7. Different Breeds, Different Purposes
  8. Animal Hybrids
  9. Cells Are Us by Dr. Fran Balkwill.
  10. Amazing Schemes Within Your Genes by Dr. Fran Balkwill.
  11. DNA Is Here To Stay by Dr. Fran Balkwill.
  12. That’s My Inheritance by William N. Pafford and Jack Rhoton
  13. Life of Mendel by Hugo Iltis

Process:

Students should look for traits by comparing themselves with their parents and siblings. Some traits to look for are listed below in a check-list format for each student. Students can download and print out a version of the check list here. Have them fill it out for themselves and then for other members of their family.

Place a check on the line if you have one of these traits.

___1.Tongue Rolling
___2. Cleft Chin
___3. Six Fingers on Each Hand
___4. Arches in Feet
___5. Dark Hair
___6. Free Ear Lobes
___7. Attached Ear Lobes
___8. Curly Hair
___9. Straight Hair
___10. Brown, Green or Hazel Eye Color
___11. Dimples
___12. Long Eyelashes
___13. Nearsightedness
___14. Farsightedness
___15. Broad Lips
___16. Webbed Fingers or Toes
___17. Straight Thumbs
___18. Long Index Finger
___19. Right Thumb Overlap*
___20. Color Blind
___21. Left Handed
___22. A Blood Type
___23. O Blood Type
___24. B Blood Type
___25. AB Blood Type
___26. Rh+ Blood
___27. Rh- Blood
___28. Cannot Roll Tongue
___29. No Cleft in Chin
___30. 5 Fingers on Each Hand
___31. Flat Feet
___32. Light or Red Hair
___33. Blue or Grey Eye Color
___34. No Dimples
___35. Short Eyelashes
___36. Normal Eyesight
___37. Thin Lips
___38. No Webbing in Hands or Toes
___39. Hitch Hikers Thumbs
___40. Short Index Finger
___41. Left Thumb Overlap*
___42. Not Color Blind
___43. Right Handed
___44. PTC Taster
___45. PTC Nontaster

*Thumb overlap is observed when one puts their hands together.

Compile a class list of traits to see what is dominant and recessive in your class. Point out to students this is a small sample for a study so they may need to do some research to discover what is a dominate or recessive trait in people.

Not all inherited traits are as simple to observe as those listed above. Hair and eye color for example are inherited however many genes control the color each of us shows to the world. The color you see is referred to as phenotype (what you can see) where as genotype is found on the chromosomes (a detailed list of traits we may or may not be able to see). Students should understand human inheritance is a complex study requiring more study.

Genetics is the study of the mechanisms of heredity. Stated another way, it is the study of the way traits or characteristics are passed on from generation to generation. People differ from each other in the expression of these traits; thus, expressing their own individuality and uniqueness. Human heredity is studied largely by means of pedigrees which are family records showing transmission of inherited traits.

The exercise provided will examine a few characteristics controlled by our genes. Each trait listed will depend upon the presence of a pair of genes called alleles. Each gene also occurs in the dominant or recessive form. A dominant gene will be expressed to produce a dominant genotype. A homozygous dominant pair would be represented by two capital letters in the genotype like DD, a heterozygous dominant pair would have one capital letter and one lower case letter, Dd, yet the dominant trait would be seen in the individual, or their phenotype. A recessive pair would have two lower case letters, dd, and the phenotype would show the recessive trait. In order to be recessive one must be homozygous for that trait. Example, you may have attached ear lobes. Since this is a recessive phenotype, you can assume that your genotype is homozygous recessive, ff. Rolling your tongue is a dominant trait so if you can roll your tongue you are showing a genotype of either RR or Rr yet your phenotype is rolling your tongue.

The student should be able to tell if they are homozygous (RR) or heterozygous (Rr) for this trait by examining the members of their immediate family. You can download a printable version of the chart here.

S1 through S4 in the chart represent your siblings.

TRAIT
Gene
Mom Dad S1 S2 S3 S4 You
Index finger
A. Short
B. Long
I
i
Thumb
A. Straight
B. Hitch-hiker
S
s
Tongue
A. Roller
B. Nonroller
R
r
Ear Lobes
A. Free
B. Attached
F
f
Thumb Overlap
A. Left On Top
B. Right On Top
L
l
PTC Taster
A. Taster
B. Nontaster
T
t

PTC is a chemically treated paper and you must decide if you will use it or not, I am told it really tastes bad, as you can tell I am a nontaster, tt.

Sex linked traits are carried on the X chromosome. Some sex-linked traits are colorblindness and the length of the ring finger.

Males have the genotype, XY where as females are XX genotype.

Discuss the work of Gregor Mendel and Thomas Hunt Morgan with your class. Mendel is considered by many to be the father of genetics. He discovered a pair of genes consisting of one dominant and one recessive trait determined characteristics in the garden pea. Later, it was discovered some genes do show incomplete dominance or blending of traits.

Mendel studied the inheritance of seven pairs of traits in garden pea plants and their seeds. For example, round vs. wrinkled seeds and tall vs. short plants. Mendel’s results were published in 1866 some 34 years after his research. Scientist found the report in 1900 and soon recognized its importance.

Thomas Hunt Morgan’s work was with fruit fly (Drosophila Melanogaster) contributing to the knowledge of sex-linked genetic traits. He chose to work with fruit flies because they are easy to grow and maintain, and it easy to observe their chromosomes with a microscope.

Fruit flies mature in about 12 days; thus you could have 30 generations within a year.

NOTE: Fruit flies provide the students the opportunity to study metamorphosis. Fruit flies go through a complete metamorphosis from egg to larvae to pupa to adult. Butterflies and moths also go through a complete metamorphosis. Grasshoppers and cockroaches go through an incomplete metamorphosis without a pupa stage. Students can try many ways to control the insect population from varying the temperature or by either adding or removing material from the fruit fly food. Do not use any chemicals harmful to the students or other organisms in your classroom.

Fast grow plants cycle in about 30 days from seed to harvest.

 

Learning Advice

Order fast grow plants and fruit flies ahead of time.

Return here to the corn observations while the fruit flies or the fast grow plants grow. Click to go to the corn journal activity. Perform the post KWL for the journal and the class.

Corn conclusion with extensions:

  1. Shell the kernels from the cob after your observations. Discuss the results from the shelling and share observations. Many times farmers in the 1930s got together and had a shelling party to produce next year’s seed. How did they know which ears of corn to select?
  2. Hybrids were developed during the late 1930s. How were these hybrids any different from the corn they shelled?
  3. Compare and contrast corn hybrids we have today.
  4. Why do we detassl corn?
  5. Imagine you own a 200-acre farm in York County, Nebraska. Describe your farm and draw a diagram showing the crop production in the 1930s. Discuss and sketch the same farm today. How has your farm changed and why? Describe your farm in the future and illustrate the changes you think will occur in your lifetime.
  6. Corn is rich in starch, a substance providing the body with energy. A simple iodine test for starch will turn black in the presence of starch. NOTE: You will need to smash the kernels before applying drops of iodine.
  7. Place corn on the food pyramid.
  8. Corn is a cereal grass related to wheat, rice, oats and barley. Research the history of corn.
  9. Based on different characteristics of the corn kernels are grouped into seven kinds: dent, flint, flour, sweet, popcorn, wax and pod. Compare and contrast these types of kernels. What kind would you plant on your farm in the 1930s?
  10. Where does Indian corn belong? Why does it have so many different colors?
  11. Corn is called zea mays. Is all corn called zea mays?
  12. Why does popcorn pop?
  13. Why do many farmers rotate their crops?
  14. The average growing season for corn varies from 4 to 6 months. What is short season corn? Why was it developed and how?
  15. Indian corn is believed to have resulted from natural hybridization. Explain this process.
  16. People to research: A short bibliography that includes their contributions to genetics. Gregor Mendel; Thomas Hunt Morgan; George H. Shull; Donald F. Jones; and George Beadle.
  17. Write a journal entry entitled, “A day in the life of a corn plant.”

 

Conclusion

Students should now start observing things like corn for similarities and differences.

Assessment Activities

  1. KWLs.
  2. Journal Assessment Rubric.
  3. Rubric for Scientific Research.
  4. Assessment Checklist for the Scientific Research.
  5. Venn Diagram.
  6. Rubric for the Research Paper.
  7. Rubric for Group Work.

 

General Notes

Remember this maybe the first time your students have thought about genetics so take it slow. The next two investigations will deal with genetics using fruit flies and fast grow plants.

If you continued with the corn study perform a KWL after each new investigation. Click here for a student investigation form.

 


Part I

Fruit Flies or Drosophila Melanogaster

Perform a KWL in the student’s journal about fruit flies, and genetics followed by a class KWL. You are now ready to explore genetics through a fruit fly investigation.

Question/Problem:

Are red eyes dominant over white eyes in the fruit fly population?

Hypothesis:

Controls:

Variable:

 

Materials

Order flies needed for the experiment from a biological supply company. They also provide food mixes and containers. If you want to make your own food you will need yeast dissolved in warm water. A ripe banana, cut about 2 inches wide should be dropped into a jar, smash the banana and add three drops of the liquid yeast into the jar. Air needs to be accessable to the flies. You may try trapping your flies with this mixture especially in the summer and autumn months. The flies you catch will more then likely be of the wild type and not a genetically pure group.

Materials Note: Flies of two different genetic variations are needed for the genetic test, I suggest red vs. white eyes since it is a trait students can see easily. The following combinations work well and if you want each group to work with a different trait order them all.

*Red eyes vs. white eyes
*White eyes vs. orange eyes
*Normal colored wild type flies vs. yellow flies
*Normal colored wild type flies vs. ebony flies
*Normal wings vs. short winged flies
*Normal wings vs. curly winged flies

This is a short list of the flies you can order from a biological catalog. There are even eyeless flies and legless flies you can order if you want to observe if these traits are dominant or recessive in fruit flies.

 

Procedure

  • Prepare or order the fly food ahead of time. Do not make it too moist.
  • If you are catching your own flies build a trap. A ripe smashed banana with three drops of yeast will attract adult flies.
  • The adults will lay eggs in the fruit that will change into larvae.
  • If you see mold growing on the banana discard. Mold is an indication no fruit flies are in your trap. When fruit flies land on fruit they introduce yeast spores, in addition to the yeast you placed on the smashed banana. The yeast allows the fermentation process to begin which lowers the pH level. The mold does not like to grow in acidic conditions. If mold does start to grow fruit flies will not want to lay eggs in that container. Fruit flies don’t eat the banana. They prefer the yeast that grows on the banana for their diet.
  • The fruit fly eggs laid by the female fly will turn into larvae (small white organisms) within a few days.
  • The larvae will feed and burrow into the fruit or climb the sides of your trap. They will turn into pupae in a few days.
  • Make sure your lid is on the trap because in a few more days you will have adult fruit flies.
  • When you have selected two types of flies for a genetic cross you must remove the flies as soon as they are produced. You do not want any uncontrolled mating to happen or you will not know for sure if your data is correct. Make observations for the trait being studied and transfer the adults to another container. Label the container so you will be able to use these flies later for a genetic test or for food supply for another classroom organism.
  • The easiest way to transfer and observe flies in the process is to place the flies in a cool environment like a refrigerator for half an hour. The cooler temperature will slow the flies down so you can dump them out on to a paper and use a small brush to move the flies around. If you have a cold plate place the flies on it to slow the process by which they warm up and fly away. Students will not have very much time to observe. They could observe after the transfer is made to a new container. A container of ice water also works well to slow the flies down for transfer and observation.
  • Bottle Biology has many ideas on building flytraps using two liter bottles. I highly recommend this book it will show students recycling is important plus it saves money on equipment.
  • Once you and your students select containers and have the food ready, you may start the investigation.

Step 1: Place red eyed flies in with white eyed flies.
Step 2: Remove flies after a few days; cool the
flies and separate them into containers. You
may want to keep all the red eyed flies in one
container and the white eyed flies in another
container. This allows you to keep the two
populations pure for this trait.
Step3: Observe the metamorphosis process, record
in the journal.
Step 4: Make predictions about the eye color for the
first (F1) generation of flies.
Step 5: Cool the flies down for about half an hour.
Place them on a cool surface.
Step 6: Observe flies and record data. Move the flies to
a new container using a small brush.
Step 7: Mark the new jar F1 generation.
Step 8: Take flies from the F1 generation or use the
new jar as a location for the F1 generation to
mate to produce the F2 generation. Remove all
F1 flies after a few days.
Step 9: Make predictions about the F2 generation’s eye
color.
Step 10: Observe the F2 generation. Transfer the
flies and label the jars F2 adult flies.

Note: The color of flies of the F1 generation will exhibit the dominate trait for eye color. Dominant traits are given a capital letter, like R for red eyes, and recessive traits are given lower case letters, like r for white eyes. A pure red eyed fly would have RR for its genotype, and a pure white eyed fly would have rr for its genotype. Genotype allows us to represent what is on the chromosomes of the fruit fly. The phenotype would be what we see, like a picture of the fly, so it is either red eyed or white eyed. A RR is referred to as homozygous dominant where as a rr is referred to as homozygous recessive. A genotype of Rr is referred to as heterozygous, meaning it has a dominant trait and a recessive trait. Some times we have a blending of traits called incomplete dominance, like when you cross a red flower with a white flower and you get all pink flowers.

A Punnett Square is a way to show the crossing of a number of traits.

Example:

Cross a homozygous dominant, RR, with a recessive, rr would look like the following using a Punnett square.

Genotypes: RR x rr

R
R

 
r

r

 

Rr
Rr
Rr
Rr

F1 generation shows 4 Rr genotypes and all four will have a phenotype of red eyes. The Rr offspring are hybrids resulting from the cross of the parents.

One parent genotype goes on the top of the square and one parent’s genotype goes on the left side of the square. The capital letter always goes in front of a lower case letter if one is present. (Capital letters are the dominant trait and the lower case letters are the recessive trait.)

Next cross two F1 flies like below: Rr x Rr

R
r

 

R

r

 

RR
Rr
Rr
rr
Genotypes:
1 = RR
2=Rr
1=rr
Phenotypes:
3=red eyes (RR, Rr)
1=white eyes (rr)

Genetic Ratio: 3:1

Try other crosses to see if you can discover the genotype and phenotypes of the offspring.

By doing the genetic crosses of the fruit flies students will be able to prove which traits are dominant and which are recessive for the fruit fly. They will be able to make a conclusion based on the data that will prove or disprove their hypothesis using the scientific process.

 

Learning Advice

Your classroom will be buzzing with activity and perhaps flies. You may want to inform others in your building about your fly experiments.

Fruit fly metamorphosis is sensitive to environmental conditions. At temperatures of 75-80 degrees F (24-27 degrees C) the life cycle takes 10-14 days.

Fruit flies are an excellent food source for praying mantis. You could have a food chain within your classroom.

 

Assessment

  1. Perform a post KWL in the student journal and do a class KWL.
  2. Journal assessment rubric.
  3. Rubric for scientific research.
  4. Checklist for the scientific method.
  5. Venn Diagram.
  6. Rubric for the research paper.
  7. Mendel worked with the garden pea plant. Based on his observation seven dominant traits were discovered. Ask students to use some of these traits to perform a cross of two plants, use a Punnett square, show genotypes and phenotypes for the offspring. G – green pea plants vs. g – yellow pea plants works well for this assessment. Use the following genotypes, GG x gg or Gg x Gg or Gg x gg for the parent plants.
  8. Explain what a hybrid is using the F1 generation of a cross between two fruit flies.
  9. What genetic hybrids were found on the farm during the 1930s?

Additional Investigation Questions:

How does the environmental temperature impact the life cycle of the fruit fly?

  1. Do fruit flies prefer certain foods?
  2. Do some fruits mold faster the others?
  3. Research how flies are controlled in our environment.
  4. Will natural chemicals, like orange peels, work to interrupt the metamorphosis process and eliminate the fly problem?
  5. Will sugar impact the fruit fly life cycle or behavior?
  6. Build an insect using a wooden clothespin as the basic structure. Create an insect that is anatomically correct. Clearly label the parts of the insect. Make a sketch of the insect in your journal.
  7. Name a new species of insect. Write a paragraph describing your insect’s adaptations to a farm environment of the 1930s, i.e., where would your insect live, what would it eat, what eats it, what is the life cycle, what are the dominant and recessive traits, and how do they aid in the insects survival.
  8. Grasshoppers invaded Nebraska during the 1930s. Research and sketch a grasshopper. What do grasshoppers eat? Why were there so many grasshoppers during the 1930s? How was the grasshopper problem solved? Locate the habitats where the grasshoppers live in the world.
  9. Write a story from the grasshopper’s point of view.

NOTE: Invertebrate animals are great classroom critters. Students enjoy and learn from observing these organisms.

Objectives for having critters in your classroom:

1. Research the natural habitat and history of an invertebrate.
2. Design a suitable habitat and maintain it in your class.
3. Research the invertebrate and share the information with the class.
4. Literature connections through invertebrate studies.
5. Investigation of the organisms using the scientific process to answer questions.
6. How does your invertebrate protect itself?

Suggested Invertebrates:

1. Ladybug – Lady Bird Beetle
2. Mealworms
3. Earthworms
4. Crayfish
5. Red Wigglers
6. Ants
7. Praying Mantis
8. Crickets
9. Brine Shrimp
10. Flour Beetles
11. Butterflies
12. Moths
13. Hissing Cockroaches
14. Daphnia
15. Fruit flies

Literature Connections:

1. Old Black Fly by Jim Aylesworth
2. “I Can’t,” said the Ant by Polly Cameron
3. The Grouchy Ladybug by Eric Carle
4. The Very Hunger Caterpillar by Eric Carle
5. I Watch Flies by Gladys Conklin
6. In the Tall, Tall Grass by Denise Fleming
7. I Wonder Where Butterflies Go In The Winter by Molly Marr
8. Amazing Insects by Lawrence Mound
9. Looking At Insects by Chris Van Allsburg
10. The Girl Who Loved Caterpillars by Jean Merril

History Connections:

1. Explore the use of corn through our history.

2. Research the oral traditions about the origin of corn as told in the stories of many Indian groups.

Math Connection:

Write to NASS Kids Agriculture and Math Fun. It includes farming statistics and games from the U.S. Department of Agriculture.

Corn:

1. The Emergence of Agriculture by B.D. Smith.
2. Food Uses of Whole Corn and Dry-Milled Fractions by L.W. Rooney and S.O. Sernaa-Saldivar.

 


Part II

Fast Grow Plants

Perform a KWL about what students know about plants and plant hybrids. Each student should record his or her KWL ideas in the journal and then help produce a class KWL.

 

Introduction

Plants, plants, plants they’re everywhere. The investigation next will deal with heredity in plants. Additional investigations will provide even more ideas for the study of plants.

The student research form provided works well for these investigations. Your students may propose a plant study or even want to develop a butterfly garden.

 

Resources

Green Thumbs Up, The Science of Growing Plants by Barbara Taylor

  • Green Thumbs Up, The Science of Growing Plants by Barbara Taylor
  • Seeds and Fruit by Daani Smit and Nicky den Hartogh
  • Fast Grow Plants – Wisconsin Fast Grow Plant Manual, Published by Carolina Biological Supply Co., 2700 York Road, Burlington, North Carolina, 27215. (1-800-334-5551)
  • Plants by David Burne

Literature Connections:

  1. How a Seed Grows by Helene J. Jordan
  2. “Magic School Bus” – Plants, Seeds
  3. Pumpkin, Pumpkin by Jeanne Titherington
  4. A Tree is a Plant by Clyde Robert Bulla
  5. Tops and Bottoms by Janet Stevens
  6. The Secret Garden by Francis Hodgson Burnett

Fast Grow Plant Information:

Fast grow plants, Biassia Rapa (Rbr) shows many variations within its population, even though the environment is relatively uniform. The genetic (genotypic) differences have been cultured so you can order seeds with all kinds of hybrid differences students may explore. Seeds can be ordered exhibiting single variables so students are not studying multiple traits at the same time. Multiple traits may be added later as their knowledge of genetics advances. You can even order seed exposed to radiation to study the impact of different amounts of radiation on the plant.

Wisconsin fast grow plants, equipment and supplies may be ordered or you may make several adaptations to save on funds. The biology class may have some of this equipment so check it out before you order.
The biology teacher should be an excellent resource person for the genetic study.

Radish, bean, grass seeds plus others work well to have students examine a given genetic type of seed for a comparison study based on observations and data collected. The fast grow plants allow your students to cross pollinate the flowers of two genetic variations, harvest the F1 generation, grow and collect data, cross pollinate that generation, harvest the seeds, plant again and harvest the F2 generation for an excellent study in hybridization in plants.

Students need to know what plants need to grow successfully. An investigation into plant requirements can begin in the Crops Section of Farming in the 1930s.

The goal here will be to explore genetics, thus we will not go into the need for light, soil, water or nutrients. Use the student investigation form and process through out the plant study. Always have the students record all information in their journal. (Click here for the student investigation form.)

Experimental Design: Question/Problem:

What plants will be developed from a cross of two genetically different plants?

Hypothesis:

Controls:

Variable:

Materials Needed:

The materials will vary depending on plants used and their growing environment.

 

Procedure

Step-by-step procedure needs to provide all the requirements the plant needs for proper growth. The procedure should be written so someone else could read it and do the same investigation.

Observations, sketches and data should be written so others can understand the results. All data needs to be in charts, tables, and graphs.

If your students use fast grow plants they will need to record data daily because they do grow fast.

 

Conclusion

The conclusion should be written which is supported by the data collected from the investigation. Usually an investigation leads to more questions, so allow the students to add these to the KWL location in their journals.

NOTE: Remember a rubric should be agreed upon between students and teacher to assess the research and presentation of information.

 

Assessment Activities

  1. Perform a KWL to see if students know traits are passed from parents to offspring.
  2. The student may create a poster and give an oral presentation to represent the science concept learned through their research.
  3. Journal Assessment Rubric.
  4. Rubric for Scientific Research.
  5. Assessment Checklist for the Scientific Research.
  6. Venn Diagram.
  7. Rubric for the Research Paper.
  8. Rubric for Group Work.
  9. Write a story about living on the farm during the 1930s. Your neighbor plants a new hybrid of corn. The plants produce more corn then any you ever observed in your years of farming in Nebraska. Will you try the new hybrid? What did it feel like to have something like hybrid plants growing in your back yard? Why did your neighbor say he would never plant anything but hybrid corn from now on?

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