Eye Color and
Polygenic Inheritance
Experiment Overview:
The purpose of this lab activity is to create a mathematical and visual example of how traits such
as eye color are passed from generation to generation. This laboratory activity will be conducted
assuming five genes code for eye color. The actual number of genes is not exactly known.
Materials:
Bingo chips, blue, 20
Bingo chips, yellow, 20
Two small beakers
Pipers, thin stem, 2
Brown paper bags, 2
White paper
Reaction plate, 48-well
Water, blue
Water, yellow
Procedure:
Part A. Determining Parental Pigmentation in Generation I
1. Obtain two brown paper bags. Label one bag male and the other female.
2. Add five blue chips to each bag and five yellow chips to each bag, for a total of 10 chips in
each bag. Shake the bag to mix the chips.
3. Without looking inside the bags draw five chips from each bag. Combine the 10 chips
drawn from the bags and count the number of blue chips. This number represents the male
parent’s gene combination. Record this number inside the (Generation I-1) square on the
Eye Color and Polygenic Inheritance Worksheet.
4. Place the 10 chips that were drawn in step 3 back into their original bags. Both the male and
female bag should each contain five blue and five yellow chips again.
5. Without looking inside the bags, draw five chips from each bag. Combine the 10 chips
drawn from the bag, and count the number of blue chips. This number represents the female
parent’s gene combination. Record this number inside the (Generation I-2) circle on the Eye
Color and Polygenic Inheritance Worksheet.
6. Before moving on to Part B, remove the original bingo chips from each bag and replace with
the genetic combination obtained for each parent in steps 3 and 5. For example, if seven blue
chips and three yellow chips were drawn in step 3, the male bag should now contain seven
blue chips and three yellow chips for a total of 10 chips.
Part B. Determining Pigmentation of Generation II, Offspring
7. Determine the genetic makeup for the first offspring (Generation II-2). Without looking, one
group member should draw five chips from the male bag and five chips from the female bag.
8. Record into their proper bags and repeat step 7 to find the number of blue chips for the
remaining offspring in Generation II (persons 3, 5, and 7).
9. The spouses of Generation II offspring were chosen at random. Fill in the phylogenetic tree
as follows.
Person
II-1
II-4
II-5
II-8
Number of Dominant Alleles
8
1
5
6
© 2008 Flinn Scientific, Inc. All Rights Reserved
Part C. Determining Pigmentation of Generation III, Grandchildren
10. Begin by determining the genetic makeup for offspring of Generation II-1 and II-2 which are
(Generation III-1 and III-2). Place the appropriate number of blue chips in the male and
female bags based on the numbers in circle (Generation II-1) and Square (Generation II-2).
Once the blue chips have been added to each bag, add yellow chips until each bag has 10
chips total.
11. Draw five chips from each bag to determine the genetic makeup (number of blue chips)
offspring using the same procedure as in Part B, step 7.
12. Repeat step 10 to determine the offspring of (Generations II-3 and II-4), (Generation II-5 and
II-6), and (Generation II-7 and II-8). Be sure to place the appropriate number of blue and
yellow chips into each bag corresponding to the parent’s scores each time. Each bag should
have a total of 10 chips.
Part D. Visualization of Phylogenetic Tree
13. Obtain 10-15 mL of both blue water and yellow water in separate small beakers.
14. Obtain a 48-well reaction plate and place it on white piece of paper.
15. A phylogenic tree will be constructed using the colored water and reaction plates. See the
diagram below to reference where each individual will be placed in the reaction plate. Exact
placement is not crucial—overall the reaction plate should represent the phylogenetic tree
with the correct parents above the correct offspring.
Generation I
Generation II
Generation III
1
2
♂
♀
1
2
3
4
5
6
7
8
♀
♂
♀
♂
♂
♀
♀
♂
1
2
3
4
5
♂
♂
♀
♀
♂
6
7
8
9
10
♂
♀
♀
♀
♂
16. Place a 48-well reaction plate on a piece of white paper.
17. Look at the numbers recorded for the first generation. If I-1 has a score of 6 (representing 6
blue chips), use a thin-stem pipet to place 6 drops of blue water and four drops of yellow
water in the appropriate well for I-1.
18. Repeat step 17 for all individuals in Generations I, II, and III.
19. Observe the difference in color between an individual with a high score versus a low score.
This phylogenetic tree is used to observe the general inheritability of eye color.
© 2008 Flinn Scientific, Inc. All Rights Reserved
Eye Color and Polygenic Inheritance Worksheet
Data Table and Observations
Post-Lab Questions and Calculations
1. Why is it necessary to return the bingo chips to the male and female bags after each draw?
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2. Look at the phylogenetic tree in the data table. How do the eye colors of the offspring in
Generation III compare to that of their parents in Generation II?
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3. In humans, tall parents tend to have tall children and short parents tend to have short
children. However, the average adult height in humans varies greatly within a population.
Why is this so?
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4. If two heterozygous individuals AaBbCc are crossed with each other, what is the probability
they will produce heterozygous offspring AaBbCc? Explain. Hint: Figure out the
probability of inheriting each gene and multiply those three probabilities together.
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5. Mendel’s Law of Independent Assortment state that allele pairs separate independently
during the formation of gametes. How is it possible for an offspring to have darker- or
lighter-shaded eyes than either of his or her parents?
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© 2008 Flinn Scientific, Inc. All Rights Reserved