Beyond Mendels Laws Incomplete Dominance A blending of

Beyond Mendel’s Laws

Incomplete Dominance • A blending of 2 traits to give an intermediate expression that can occur in heterozygous individuals. • Neither trait is dominant. • Ex. A red flower and a white flower make a pink flower.

• • CR = red, CW = white CR CR is necessary to produce a red flower CW CW’ produces a white flower CR CW individuals with only one CR are unable to make enough red pigment to produce red flowers, so they appear pink.

• Ex. If a white flower was pollinated by a pink flower, what might the offspring look like?

Co-dominance • Both alleles are expressed in the heterozygous individual. • Both alleles are dominant. • Ex. Feather colour in chickens.

• BB produces black feathers. • WW produces white feathers. • BW produces black and white feathers.

• Ex. If two chickens, both that were black and white, mated, what might the offspring look like?

Multiple Alleles • When genes have more than 2 alleles. • Ex. Human blood types

• Three alleles are involved: A, B, and O, expressed as IA, IB, and i. IA and IB are dominant over i. • IA and IB are co-dominant and are expressed equally (Type AB blood).

• Ex. If a man who has type A blood (heterozygous) mated with a woman who has type B blood (heterozygous), which blood types might the children have?