Download CO-DOMINANCE/INCOMPLETE DOMINANCE – Worksheet #2 Name

Mendelian Genetics: “Exceptions”
Name_______________________
Block____
1. Explain the difference between incomplete and codominance.
Co-Dominance Problems
2. In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the allele for
white is W. The heterozygous phenotype is known as erminette (black and white spotted).
a. What is the genotype for black chickens? ____
b. What is the genotype for white chickens? ____
c. What is the genotype for erminette chickens? ____
3. If two erminette chickens were crossed, what is the probability that:
a. They would have a black chick? ____%
b. They would have a white chick? ____%
Parents: ____ X ____
4. A black chicken and a white chicken are crossed. What is the probability that they will have erminette chicks? ____%
Parents: ____ X ____
In shorthorn cattle, when a red bull (RR) is crossed with a white cow (WW), all the offspring are roan—a spotted, red
and white or milky red color.
5. What offspring are expected from mating a roan bull and a roan cow?
6. What phenotypes would you expect from a cross between a red bull and a white cow?
Blood type is controlled by 3 alleles: A, B, O. A & B are codominant, O is recessive.
7. 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? __________________
8. 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 HOW YOU DETERMINED THIS BELOW
9. 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 HOW YOU DETERMINED THIS BELOW
10. A woman with type A blood (genotype AO) is married to a type B person (genotype BO). What proportion of their
children will have:
A blood? _______ B blood? ______ O blood _____ AB blood ________
SHOW HOW YOU DETERMINED THIS BELOW
11. 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? _____
12. 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 the crosses)
Incomplete Dominance Problems
13. In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R)
and white (W). The heterozygous genotype is expressed as pink.
a. What is the phenotype of a plant with the genotype RR? ___________
b. What is the phenotype of a plant with the genotype WW? ___________
c. What is the phenotype of a plant with the genotype RW? ___________
14. A pink-flowered plant is crossed with a white-flowered plant. What is the probability of producing a pink-flowered
plant? ____%
Parents: ________ X ________ SHOW THE CROSS BELOW
15. What cross will produce the most pink-flowered plants? Use a punnett square to support your answer.
Parents: _______ X _______
16. In Andalusian fowls, black individuals (B) and white individuals (W) are homozygous.
A homozygous black bird is crossed with a homozygous white bird. The offspring are all bluish-gray. Show the cross as
well as the genotypes and phenotypes of the parents and offspring.
17. What results if a black individual is crossed with a bluish-gray individual? (SHOW YOUR WORK)
18. If two bluish-gray individuals were crossed, what would be the ratios for both phenotype and genotype of the
offspring? *remember to label!! Include your Punnett square below
Phenotypic ratio:
Genotypic ratio: