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

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

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

Incomplete Dominance and Co-Dominance

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

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

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

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

Other ways to represent incomplete dominance

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

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

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