Non Mendelian Genetics Patterns of inheritance that aren’t simply dominant or recessive

I. Incomplete Dominance

II. Co-dominance A.The phenotypes of both homozygotes are produced in the heterozygous individuals; both alleles are expressed equally. B. Examples 1. Short-horned cattle – red and white coats are co- dominant whiteo oiat 2. Chickens – feather color; black and white are co- dominant 3. Four o’clock plants – red and white petals are co- dominant

Short-horned cattle Four o’clock plants Black and white feathers

III. Multiple Alleles A.Traits controlled by more than 2 alleles. B. Examples 1. ABO blood type in humans – A and B are codominant, but dominant to O 2. Pigeons – feather color; B A, B and b; B A produces ash red feathers, B produces wild-type (grey) feathers, and b produces chocolate colored feathers

IV. Polygenic Inheritance A.Many traits are controlled by 2 or more genes. B. Examples: 1. Eye color 2. Hair color 3. Skin color 4. Height

Eye Color

Skin Color

V. Traits Influenced by the Environment A.An individuals phenotype often depends on conditions in the environment. B. Such factors as temperature, amount of sunlight, soil conditions and nutrition can affect the phenotype of an organism. C. Examples: 1. Arctic fox – brown in summer; white in winter 2. Hydrangea flower color – acidity of the soil determines blue or reddish color 3. Siamese cats – cooler body areas are darker 4. Height in humans - early nutrition (or lack of) affects the height of humans

The End!