1. Test Cross- Unknown Genotype
Is the purple plant homozygous or heterozygous ?
Perform a test cross!
Always! Cross the unknown with a homozygous recessive

2. Practice! P F1 ? x gg g g G g G g Phenotype: 100% green Genotype:
Key:
G=green
g= yellow g G g G g F1
Phenotype:
100% green
Genotype:
100% heterozygous g G g G g

3. Practice! ? P F1 ? x gg Phenotype: 50% green 50% yellow Genotype: Key:
G=green
g= yellow F1
Phenotype:
50% green
50% yellow
Genotype:

4. Incomplete Dominance and Co-Dominance

5. Incomplete Dominance Neither allele is dominant
In some cases, an intermediate phenotype is shown

6. Snapdragons
In snapdragons, flower color can be red, pink, or white. The heterozygous condition results in pink flowers rr Rr RR

7. Incomplete Dominance Cross
Key:
R= Red
r= White
F1 Phenotype:
100% pink
F1 Genotype:
100% heterozygous Rr

8. F1 Cross Key: R= Red r= White Phenotype: 1:2:1 25% Red 25% White
50% Pink
Genotype: 1:2:1
25% homozygous RR
25% homozygous rr
50% heterozygous Rr

9. Other ways to represent incomplete dominance

10. Co-dominance Both alleles are expressed equally
Neither allele is more dominant than the other
Erminette chickens
Roan Cows

11. Co-Dominance Erminette Chicken
Key:
B =Black
B1 = White
Co-Dominance Erminette Chicken B B B1 B B1 B B1 B1 B B1 B B1
P generation
Black chicken X White chicken
F1 generation = erminette (checkered patterned)
Phenotype: 4:0 or 1:0
100% erminette
Genotype: 4:0 or 1:0
100% heterozygous

12. Erminette chicken BB BW BB BW Key: BB =Black BW = White Key: B= Black
B2 = White B2 B1 B2 B2 B2