1. Notes: Incomplete/Codominance
(page 12)

2. Notes: Incomplete/Codominance
(page 12)
• So far, we have learned about simple
Mendelian inheritance--traits controlled by
dominant and recessive paired alleles

3. Notes: Incomplete/Codominance
(page 12)
• So far, we have learned about simple
Mendelian inheritance--traits controlled by
dominant and recessive paired alleles
• However, MOST alleles are not simply
dominant or recessive

4. • Incomplete Dominance = The phenotype of
the heterozygote is intermediate between
those of the two homozygotes

5. Example: Snapdragons
• RR = Red

6. Example: Snapdragons
• RR = Red
• WW= White

7. Example: Snapdragons
• RR = Red
• WW= White
• RW = Pink

8. Example: Hair
• CC = Curly SS = Straight CS= Wavy

9. Example: Hair
• CC = Curly SS = Straight CS= Wavy
• Punnett square problem: 2 Wavy haired
peoplehave a child
C S
C
S

10. Example: Hair
• CC = Curly SS = Straight CS= Wavy
• Punnett square problem: 2 Wavy haired
people marry
C S
C CC CS
25% Curly
S CS SS 50% Wavy
25% Straight

11. Practice Problem: Incomplete
Dominance (pg 13)
• For each practice problem, draw the Punnett
square and give the phenotype ratios
A: Cross a pink snapdragon with a white
snapdragon
B: Cross a red snapdragon with a white
snapdragon

12. (pg 12)
• Codominance = the heterozygote produces
the phenotypes of BOTH homozygotes

13. Example: Chickens
• BB = Black
• WW = White

14. Example: Chickens
• BB = Black
• WW = White
• BW = Checkered

15. Other examples
Cows:
RR = Red
WW= White
RW=Roan (red and white spots)
Horses:
GG = Gray
WW = White
GW=Apaloosa (white with gray spots)

16. • Punnett square problem: 2 appaloosa horses
are crossed
G W
G
W

17. • Punnett square problem: 2 appaloosa horses
are crossed
G W
G GG GW
25% Gray
W GW WW 50% Appaloosa
25% White

18. Codominance Practice Problem (pg 13)
• For each practice problem, draw the Punnett
square and give the phenotype ratios
A. Cross a checkered chicken with a black
chicken
B. Cross two checkered chickens together

19. Output Activity (pg 13)
• Make up an incomplete/codominance
problem that requires a Punnett square to
solve. You must make up a NEW trait, and
explain the phenotypes of the homozygotes
and the heterozygotes in the problem.