1. Codominance & Incomplete Dominance
Genetics
Codominance & Incomplete Dominance

2. Warm up What happens if you mix yellow paint with blue paint?
How could this be used as an analogy to describe the inheritance of certain traits?

3. Exceptions in Inheritance of Traits
Not all traits are inherited as dominant or recessive from a single gene (pair of alleles).
Incomplete dominance
Codominance
One gene, many traits
Many genes, one trait
Environmental impact

4. One Gene, Many Traits
Sometimes, one gene influences more than one trait.
Ex: white tiger
Gene for white fur also causes blue eyes

5. Many Genes, One Trait
Some traits are the result of several genes acting together.
Ex: color of your skin, hair, and eyes
Difficult to tell if the traits are a result of a dominant or recessive allele.
At least two genes determine human eye color. That’s why many shades of a single color are possible.

6. The Importance of Environment
A dog with the genes for long fur could have its fur cut short.
You may have the genotype to grow tall, but you need a healthy diet to reach your full height.

7. Foldable
Incomplete Dominance
Codominance

8. Codominance Co = together
Red x White = Red & White
Co = together
coexist (exist together)
cooperate (work together)
In codominance, both traits appear (both traits are equally dominant)

9. Punnett Square ExampleCR CR
C = color
CRCR = red
CWCW = white
CRCW = red & white CW
CRCW
CRCW CW
CRCW
CRCW
Parents with two different phenotypes produce offspring with a third phenotype.
Both parents’ traits show up together in the offspring.

10. Another Example of Codominance

11. Other Codominance Examples
Cattle
Red x White = Roan
Human Blood Types
A x B = AB

12. Incomplete Dominance
Incomplete dominance – produces a mixing or blend of the two traits
Red x White = Pink

13. Punnett Square Example
RR = red
WW = white
RW = pink W RW RW W RW RW
Parents with two different phenotypes produce offspring with a third phenotype.
Both parents’ traits show up together in the offspring.

14. Another Example of Incomplete Dominance
Horses
Chestnut brown x creamy white = palomino

15. Practice: Codominance & Incomplete Dominance
Incomplete and Codominant practice worksheet.doc