1. Exploring Mendelian Genetics
Chapter 11, Section 3

2. The Complexity of Inheritance
Mendel studied simple characteristics in pea plants and was able to define some basic principles behind their inheritance patterns
However, many characteristics visible in organisms have more complex inheritance patterns than those studied by Mendel

3. Incomplete Dominance r w rw
Pink
Neither allele is dominant over the other, therefore the heterozygous phenotype is an intermediate (or BLEND) of the two homozygous phenotypes

4. Codominance R W RW
Roan
Both alleles are visible in the heterozygous phenotype
Ex: Roan Coat (both red and white hairs)
AB blood (both A and B antigens)

5. Multiple Alleles When there are more than 2 alleles in the population
Phenotype
Genotype A
IAIA, IAi B
IBIB, IBi AB
IAIB O ii
When there are more than 2 alleles in the population
Ex: Blood Type (IA, IB, i)
Coat color in Rabbits
(C, cch, ch, c)

6. Polygenic Inheritance
When two or more genes control the trait
The more genes that control the trait, the more variation in phenotypes
Ex: Height, eye color, skin color in humans
Feather color in parakeets
Green
Blue
Yellow
White
BBYY
BByy
bbYY
bbyy
BbYY
Bbyy
bbYy
BBYy
BbYy

7. The Environmental Influence
Environmental factors (such as temperature, sun exposure, altitude, diet, exercise, etc.) can have significant effects on the phenotypes of certain organisms
In general, the product of a genotype is not typically a defined phenotype, but rather a range of possibilities influenced by the environment.