Codominance, Incomplete Dominance, and Multiple Alleles!
Name _______________________________ Block __________ Date ________
Let’s try our luck at some problems involving codominance and incomplete dominance!
Remember that codominance is when we see 2 alleles expressed at the same time
individually in the phenotype. Incomplete dominance is the blending of the two alleles as a
phenotype.
Codominance
* Birds can be blue, white, or white with blue-tipped feathers.
*​
Use these Letters:
B
Blue = C​
W
White = C​
What would the genotype be for each of the combinations listed above?
Blue ________
White with blue-tips _______
White ________
Let’s do a punnett square to figure out what would result from a cross between a White
bird and a White with blue-tipped feathered bird. Write the cross and do the punnett
square!
Cross: _______ X ________
What are the possible genotypes? _________________________
What are the possible phenotypes? ________________________
What is the probability they will have a Blue offspring? ________________
What is the genotypic ratio? _________ What is the phenotypic ratio? ___________
Let’s do one more!​
What would be the result if we crossed a White bird with a Blue bird?
Set up the cross and answer the questions.
Cross: ______ X _______
What are the possible genotypes? __________________________
What are the possible phenotypes? _________________________
What is the probability they will have a Blue offspring? ________________
What is the genotypic ratio? _________ What is the phenotypic ratio? ___________
Here’s a different scenario! Let’s look at some flowers!
W
R
Flowers can be white, pink, or red. ​
Please use these letters:​
White = C​
Red = C​
What would the genotypes be for each of the following phenotypes?
White _______
Pink ______
Red _______
What would the cross be between two Pink flowering plants? Write the cross and do the
punnett square!
Cross ______ X ________
What are the possible genotypes? __________________________
What are the possible phenotypes? _________________________
What is the probability they will have a White offspring? ________________
What is the genotypic ratio? _________ What is the phenotypic ratio? ___________
Incomplete dominance
Look at the examples for the Sneeches! Pay close attention to the letters used to
represent the alleles and use those letters to answer the punnett squares and
questions.
A Sneech can be tall, medium, or short.
The alleles you will use for height are:
H = tall
h = short
What would the genotype be for:
Tall ________
Medium _______
Short _______
Try this! Two medium height Sneeches are trying to figure out what the odds of
them having a tall offspring would be. Set up the cross and tell what the potential
outcome would be for them!
Cross: _______ X _______
What are the possible genotypes? _____________________
What are the possible phenotypes? ____________________
What is the probability they will have a tall offspring? ________________
What is the genotypic ratio? _________ What is the phenotypic ratio? ___________
Continue to next page...
In Smileys, eye shape can be starred, circular, or a circle with a star.
Write the genotypes for the pictured phenotypes
Use these letters:​
Circle = E
Star = e
Genotype: _______
_______
_______
Show the cross between a star-eyed and a circle eyed. Cross; _____ X _____
What are the phenotypes of the offspring? ____________
What are the genotypes? __________
What is the genotypic ratio? _________ What is the phenotypic ratio? ___________
Show the cross between two circle-star eyed. Cross _____ X ______
How many of the offspring are circle-eyed? ____________
How many of the offspring are circle-star eyed? ____________
How many are star eyed? ____________
Genetics: Multiple Allele Traits
Blood Type
Blood type is controlled by 3 alleles: A, B, O.
A & B are codominant, O is recessive.
1. a) What are the two genotypes possible for a person who as A blood? ___________
b) What genotype does a person with AB blood have? _______________
c ) What genotype does a person with O blood have? _____________
d) What are the two genotypes possible for a person who as B blood?_____________
2. A man with type AB blood is married to a woman also with type AB blood. What
percentage of their children will have:
A blood? _______ B blood? ______ O blood _____ AB blood ________
Show your work:
3. A man has type B blood (genotype BB) is married to a woman with type O blood. What
blood type will all their children have? ________
What is the genotype of the children? ______
Show your work:
Continue to next page...
5. A woman with type A blood is claiming that a man with type AB blood is the father of her
child who is type B.
Could this man be the father of the child? _______________
Show the possible crosses; remember that the woman can have AA or AO genotypes.
Assuming that he is the father, what must the mother's genotype be? _____
6. A man with type AB blood is married to a woman with type O blood. They have two
natural children and one adopted child. Jane has type A blood, Bobby has type B blood,
and Grace has type O blood.
Which child was adopted? ____________________
Show your work to provide support for your answer!