1. Beyond Dominant & Recessive Alleles
Heredity
Beyond Dominant & Recessive Alleles
Incomplete Dominance & Codominance

2. Learning Goals
1. Describe incomplete dominance. Describe codominance. 2. Compare and contrast incomplete dominance and codominance. Give 2 similarities and 1 difference. 3. Explain how letters are chosen when doing Punnett square problems for incomplete dominant and codominant traits

3. Beyond Dominant and Recessive Alleles
Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes. This power point will address traits that are neither dominant nor recessive. The rest you will learn later in high school.

4. Incomplete Dominance 
Incomplete dominance - when one allele is not completely dominant over another.
Heterozygous genotype = BLEND
Since one allele is not completely dominant over the other allele, we use two different capital letters to represent the alleles

5. Example: Snapdragons
Example: A cross between red (RR) and white (WW) snapdragons produces pink flowers (RW).
The colors blend to make pink.

6. How incomplete dominant genotypes are written
As you probably noticed, incomplete dominant genotypes use only capital letters.
Remember: Heterozygous (hybrid) traits that express incomplete dominance are represented by two different capital letters.

7. Homozygous RR
(Red)
Heterozygous RW
(Pink)
Homozygous WW
(White)

8. Another Example of Incomplete Dominance
Baaaaaaaa!

9. Codominance 
Codominance - both alleles contribute to the phenotype. No blending.
Heterozygous genotype = both traits appear
Since one allele is not completely dominant over the other allele, and both traits appear together, we use two different capital letters to represent the alleles

10. Codominance in Chickens
Example: A cross between black (BB) and white (WW) chickens produces chickens speckled with black and white feathers (BW).

11. Roan Cows
Codominance- unlike red and white snapdragons, both the red and white are expressed in cows. They are not blended to make a “pink” cow.

12. Roan Horse
Draw a punnett square to show how this roan horse got its trait.

13. Other Codominant Phenotypes

14. More Codominance Examples
Bird wings
Flowers

15. Just kidding! You get the idea…..

16. Codominance in Humans Sickle Cell Anemia
The altered form of hemoglobin that causes sickle-cell anemia is inherited as a codominant trait.

17. Learning Goals
1. Describe incomplete dominance. Describe Codominance. 2. Compare and contrast incomplete dominance and codominance. Give 2 similarities and 1 differences 3. Explain how letters are chosen when doing punnett square problems for incomplete dominant and codominant traits

18. Whiteboard Practice
Step 1: Is the example showing Incomplete Dominance or Codominance??????
Step 2: You will be given the 3 phenotypes, Write the corresponding genotypes.
2 alleles (1 from mom, 1 from dad)
Use the 1st letter for each trait
Both letters are capitol
Step 3: Set up and fill-in a punnett square. Calculate percent probability for ALL 3 TRAITS!!!

19. Let’s do the 1st one together 
Birds can be blue, white, or white with blue-tipped feathers
1. Incomplete Dominance or Codominance?
2. Genotypes:
blue-
white –
blue-tipped –
3. Show a cross between a white and blue-tipped bird

20. Practice Identifying A cat can be black, tan, or tabby (black & tan)
1. Incomplete Dominance or Codominance?
2. Genotypes:
black-
tan –
tabby –
3. Show a cross between a heterozygous tabby and tan cat

21. Practice Identifying A Who can have curly hair, spiked hair, or wavy
1. Incomplete Dominance or Codominance?
2. Genotypes:
curly-
spiked –
wavy-
3. Show a cross between a curly and wavy Who

22. Practice Identifying A sneech can be tall, short, or medium
1. Incomplete Dominance or Codominance?
2. Genotypes:
tall-
short –
medium –
3. Show a cross between two heterozygous sneeches

23. Practice Identifying
A horse can be black, white, or roan (black & white)
1. Incomplete Dominance or Codominance?
2. Genotypes:
black –
white –
roan -
3. Show a cross between a heterozygous roan and black horse

24. Practice Identifying Flowers can be white, pink, or red
1. Incomplete Dominance or Codominance?
2. Genotypes:
white-
pink –
red-
3. Show a cross between a white and red flower