Peabops!
An exercise in plant genetics
Making the Peabop Grandparents
Each student will make a "plant", called a Peabop. Just as Gregor Mendel did, you will
start with two grandparent plants that are pure breeding for each of four traits.
1. Pick who is going to be grandparent 1, who will be grandparent 2, who will be
grandparent 3 and who will be grandparent 4. Write that information above the column
for the grandparent that you will make.
2. Fill out the chart for each grandparent. Grandparent 1 & 3 should be 1,1 for all
traits. Grandparents 2 & 4 should be 2,2 for each trait.
3. Choose the appropriate stem. If your plant is 1,1 then you need a long pipe
cleaner, and if it is 2,2 you need a short one, according to the key to traits.
Remember, each pair of students needs to produce one plant that is 1,1 for each of
the four traits and another plant that is 2,2 for those same four traits.
4. Do the same for the color of flower, color of seed and position of flower.
5. Put the peabops out on a table near you.
Key to Traits
Trait
Variation
Genotype
stem length
stem length
tall
short
1,1 or 1,2
2,2
color of flowers
color of flowers
purple
white
1,1 or 1,2
2,2
position of flowers
position of flowers
end of branch
midbranch
1,1 or 1,2
2,2
color of seed
color of seed
yellow
green
1,1 or 1,2
2,2
B. Making the Peabops Parents
Picking the chromosomes to make the parents
1. Find labeled strips of paper representing the chromosomes carrying the appropriate
combination of genes for your plant, two strips for each trait and a total of eight for
each plant. Each pair of chromosomes should be a different color (for identification
purposes). Turn the pairs face down
2. Now each pair of students will breed their 1,1 grandparent plant with their 2,2
grandparent plant. Randomly choose one chromosome (paper strip) from each
pair from the grandparent 1,1 plant and combine them with chromosomes randomly
chosen (one from each pair) from the grandparent 2,2 plant.
3. Put all of the “extra” chromosomes in the envelope. These are the eggs and
sperm that don’t make a baby. The chromosomes that you chose are combined and
carry the genes for a cross-bred plant which is 1,2 for all of the traits.
4. Using the Key to Traits, build a Peabop plant with all of the appropriate traits.
These are the Peabop parents! Each group of four should have two Peabop parents
(kids of the grandparents.) Put them on a table near you.
C. Making the Grandkid
Picking the chromosomes to make the grandkid
5. Now take the chromosomes (and their genes labeled on them) for the two Peabop
kids that have been produced by your group of four students and randomly select
one chromosome of each pair for each trait from each of the Peabop kids. These
“new” chromosome pairs carry the genes for a Peabop grandkid!
6. Now build a Peabop grandkid using the information on the chromosomes that you
have selected and compare all of the Peabop grandkids in the class.
Student Questions
1) When you were making pea kids and grandkids, you took one of each pair of
chromosomes from a parent. In this way, you are simulating the making of egg and
sperm cells. You studied this process earlier in the unit, but now you have included
the genes found on those chromosomes. How does the number of chromosomes in
an egg or sperm cell compare to the number of chromosomes in the parent cells?
2) How do the number of chromosomes in the cells of the parents compare to the
number of chromosomes in the cells of the grandparents?
3) Why do you have variation (differences) in the “grandkids”?
PEABOPS
Names_________________________
__________________________
Write what the pea plant looks like as well as the genes it has (in numbers)
Grandparent 1
(1,1)
Grandparent 2 Grandparent 3 Grandparent 4
(2,2)
(1,1)
(2,2)
Height:
Flower Color:
Pea Color:
Placement of
Flower:
Kid 1
Kid 2
Height:
Flower Color:
Pea Color:
Placement of
Flower:
Grandkid
Height:
Flower Color:
Pea Color:
Placement of Flower:
Grandkids
Write what the pea plant looks like as well as the genes it has (in
numbers)
Height
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8
Flower
Color
Pea Color
Placement of
Flower
Key to Traits
Trait
Variation
Genotype
stem length
stem length
long
short
1,1 or 1,2
2,2
color of flowers
color of flowers
purple
white
1,1 or 1,2
2,2
position of flowers
position of flowers
end of branch
midbranch
1,1 or 1,2
2,2
color of seed
color of seed
yellow
green
1,1 or 1,2
2,2
Tall (1)
Stem
Short (2)
Stem
Tall (1)
Stem
Short (2)
Stem
Tall (1)
Stem
Short (2)
Stem
Tall (1)
Stem
Short (2)
Stem
Tall (1)
Stem
Short (2)
Stem
Tall (1)
Stem
Short (2)
Stem
Purple (1)
Flower
White (2)
Flower
Purple (1)
Flower
White (2)
Flower
Purple (1)
Flower
White (2)
Flower
Purple (1)
Flower
White (2)
Flower
Purple (1)
Flower
White (2)
Flower
Purple (1)
Flower
White (2)
Flower
End of
Branch (1)
(1)
Middle of the
branch (2)
End of
Branch (1)
Middle of the
branch (2)
End of
Branch (1)
Middle of the
branch (2)
End of
Branch (1)
Middle of the
branch (2)
End of
Branch (1)
Middle of the
branch (2)
End of
Branch (1)
Middle of the
branch (2)
Yellow Pea
(1)
Green Pea
(2)
Yellow Pea
(1)
Green Pea
(2)
Yellow Pea
(1)
Green Pea
(2)
Yellow Pea
(1)
Green Pea
(2)
Yellow Pea
(1)
Green Pea
(2)
Yellow Pea
(1)
Green Pea
(2)