Codominance Practice Problems - Weebly



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Codominance/Incomplete Dominance Practice Problems

• Complete all crosses using and superscript notation for blood type and other codominant traits.

• Codominant alleles are notated with a capital initial and superscript. (ex: IAIB for AB blood type) recessive alleles are written as the lowercase initial (ex: ii for O blood type)

1. Mom has type A blood. Dad has type AB blood. What possible blood types could their children inherit? (Show all possibilities).

2. Mom has type O blood. Dad has type AB blood. What percentage of their kids will inherit type B blood?

3. Mom has type B blood. Dad has type O blood. They have a child with type O blood. Make a punnett square to show what Mom’s genotype must be to have a child with type O blood.

4. A woman sues a man for child support, claiming that he is the father of her illegitimate child. The woman is type A, the child is type O, and the man is type AB. Could he be the father of her child? Show why or why not.

5. A wealthy elderly couple dies together in an accident. A man comes forward, claiming that he is their long lost son and is entitled to their fortune. The couple were of blood types AB and O. The man has type O blood. Could he be the heir to the fortune? Show why or why not.

6. John has type O blood. He knows his mother had type B blood. He does not know the identity of his father, however. What possible blood types could his father have had? Show your work.

7. Mike has type AB blood. Paul has type O blood. Mike knows that his Mom had type B blood. Show how it could be possible for Mike and Paul to be brothers.

8. Mom’s genotype is IAi and she is Rh negative. Dad’s genotype is IA IB and he is heterozygous for the Rh factor. Use a dihybrd cross to show the inheritance of blood type in their children.

9. You can use the same notation we see in blood type for other codominant traits as well. In cows, the red and white coat color alleles are codominant. We can choose an initial to represent this trait, like “C” for coat. Then we can give the codominant alleles superscripts.

Show a cross between a white cow (CWCW) and a red cow (CRCR)

Note: When selecting an initial to represent a codominant trait, do not use X, Y, or I. X & Y are specific to sex chromosome inheritance and I is specific to blood type.

11. In chickens, black and white feather color are codominant alleles for this trait. Using superscript notation, show a cross between two black and white feathered chickens (erminette).

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