1. Genetics Beyond Mendel
Types of Dominance
Genetics Beyond Mendel

2. Complete Dominance All of the problems we’ve studied so far
One allele is completely dominant over another
BB=brown hair
Bb=brown hair
bb=blonde hair

3. Heterozygous
In complete dominance, the heterozygous form always expresses the dominant trait
However, not all traits exhibit complete dominance

4. Other Types of Dominance
Incomplete Dominance
Codominance

5. Incomplete Dominance
In the heterozygous form, there is a blend of traits
Ex: Draw a punnett square to cross a Dark Purple flower with a White flower.
PP X pp

6. Resulting Offspring Genotypes? Phenotypes? (physical characteristics)Pp
Phenotypes? (physical characteristics)
Hint: NOT Dark Purple
A BLEND of Dark Purple and White…
Light Purple!!!

7. Codominance Both traits are Dominant
Heterozygous form expresses BOTH traits
Ex: Cross a PP X pp
Offspring: Pp, we see BOTH traits
Purple and white stripes!!!

8. Codominance in Humans Blood Types
What type are you? (don’t worry about positive or negative for now)
A, B, AB, O

9. Types and Possible Genotypes
Blood Type
Possible Genotype(s) A
AA, AO B
BB, BO AB O OO

10. Which is/are dominant?
Dominant: A and B
Recessive O

11. What do the types mean?

12. Note for blood transfusions:
Because of antibodies
A can only receive type A or O
B can only receive type B or O
AB can receive A, B, AB or O
Universal Recipient (can receive all)
O can receive O only
Universal Donor (can donate to all)

13. Codominance
A woman with type A marries a man with type B. They are both heterozygous. What types of blood can their children have? Draw a Punnett Square.

14. Incomplete dominance
Two gray bunnies (incomplete dominance) have a litter of bunnies. What are the possibilities for their offspring? Draw a Punnett Square

15. Jerry, Jerry, Jerry!
A woman takes two possible fathers of her child to the Jerry Springer show for a paternity test. Based on their blood types, who do you think is the father? Show your work!
Mom- Type A
Child-Type O
Dad 1- Type AB
Dad 2-Type B