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Genetics Unit: “Tall Short Green Yellow”
Basics
We will do another simulation of heredity and genetics. Pretend that we have two populations of
the same species of plant. In the first population the plants are all tall with green seed pods.
These plants have been breeding among each other for a very long time and carry only the
inheritance factors for tallness and green seed pods. In the second population the plants are all
short with yellow seed pods. These plants have been breeding among each other for a very long
time and carry only the inheritance factors for shortness and yellow seed pods.
We will breed the parent (P) generation by taking one sex cell from a plant from the first
population (P1) and combining it with a sex cell from the second population (P2). The gene for
height in the sex cells will be represented by beans. Dark beans will represent the allele T for
tallness and light beans will represent the allele t for shortness. The gene for seed pod color in
the sex cells will be represented by split peas. Green split peas will represent the allele G for
green seed pods and yellow split peas will represent the allele for yellow seed pods.
Tallness T and green seed pods G are both dominant.
When breeding P1 and P2 to create the F1 generation we get all members of the F1 generation
with the phenotype tall with green pods and the genotype heterozygous (Tt) for height and
heterozygous (Gg) for pod color.
In this lab you will simulate the breeding of the F1 generation with itself to produce the F2
generation and see what phenotypes and genotypes occur, and in what percentages they occur.
Students will work in pairs. Each student will turn in a lab report written in our standard format.
Problem
What percentage of plants in the F2 generation will have the phenotype:
tall and green,
tall and yellow,
short and green,
short and yellow?
What percentage of plants in the F2 generation will have the genotype:
dark, dark, green, green
TTGG
dark, dark, green, yellow
TTGg
dark, light, green, green
TtGG
dark, light, green, yellow
TtGg
dark, dark, yellow, yellow
TTgg
dark, light, yellow, yellow Ttgg
light, light, green, green
ttGG
light, light, green, yellow
ttGg
light, light, yellow, yellow ttgg?
Genetics Unit: Tall Short Green Yellow, Page 1, Printed 6/24/17
Hypothesis
Record your tentative answers to the questions posed above before conducting the experiment.
Safety
There are no safety concerns for this activity.
Materials
48 dark colored beans
48 light colored beans
48 green split peas
48 yellow split peas
4 paper cups
Clean up
Return all supplies as you found them when you are done.
Procedure for Producing the F2 Generation
Follow these steps:
1. Place 24 dark colored beans and 24 light colored beans in cup #1. Mix thoroughly. Do the
same for cup #2. These will represent the genes for height present in the F1 generation.
2. Place 24 green split peas and 24 yellow split peas in cup #3. Mix thoroughly. Do the
same for cup #4. These will represent the genes for seed pod color present in the F1
generation.
3. Place cups 1 and 3 off to one side. Place cups 2 and 4 together off to the other side, away
form cups 1 and 3.
4. Close your eyes and take one bean from cup 1 and then one pea from cup 3. Place these
together, representing the alleles for height and pod color in the gamete from one parent.
5. Repeat for cups 2 and 4, representing the alleles for height and pod color in the gamete
from the other parent.
6. Place the two gametes near each other, representing sexual reproduction and the
production of a zygote that will grow into a plant of the F2 generation.
7. Record the phenotype and genotype of the plant that would grow from the zygote.
8. Put the beans and peas back into the cups from which they came. Cover and shake each
cup. Repeat the process 99 more times.
Genetics Unit: Tall Short Green Yellow, Page 2, Printed 6/24/17
Data
Record your data in a table numbered Table 1 and given an appropriate title.
Data Analysis
Calculate and record the percentages of each phenotype and genotype produced in the F2
generation.
Conclusion
Using your data and analysis answer the questions posed in the problem. Compare to your
hypothesis.
Uncertainty
Discuss all sources of uncertainty in this investigation. Be specific.
Follow-up Questions
1. Create a Punnett Square that describes this experiment. What are the percentages of each
phenotype and genotype predicted by the Punnett Square?
2. Get a copy of the sheet titled “Tall Short Green Yellow Data Summary.” Fill this out and
turn it in. The instructor will collect these data summaries from each lab group and make
the collected class data available to all students. Did all student groups get the same data?
Why or why not?
Optional Advanced Work
I. Incomplete Dominance
Do internet/library research on incomplete dominance. Present your work in one of the following
ways:
1. Write a short (1-2 pages) review of the what you learned. OR
2. Make a PowerPoint or similar presentation summarizing incomplete dominance. OR
3. Give a short (3-5 minute) presentation to your classmates. OR
4. Arrange a private meeting with the instructor outside of class to discuss your work.
II. Further Data Analysis
Gather all data from your class. Calculate percentage errors from the total class data compared to
the theoretical predictions.
Genetics Unit: Tall Short Green Yellow, Page 3, Printed 6/24/17
What to Do if You Missed This Lesson
If you missed the class sessions when the performed this simulation, you have two choices:
1. Find a friend any have him/her explain what we did. Copy the friend’s data and proceed
with your lab report. Please state on your lab report whose data you borrowed.
2. Find another student who was present for this simulation and is willing to do the
simulation with you at a time outside of class.
3. If you missed multiple lessons and/or had extenuating circumstances such as a Bar/Bat
Mitzvah, extended illness, or family trip, meet with the instructor outside of class to
discuss a plan.
References: Genetics and Evolution Science Fair Projects, Robert Gardner, Enslow, Berkley
Heights NJ, 2005.
Genetics Unit: Tall Short Green Yellow, Page 4, Printed 6/24/17