1. 11.3 Other Patterns of Inheritance

2. Beyond Simple Dominance Not all genes show simple patterns simple patterns of inheritance Most genes have more than two alleles or are controlled by more than one gene

3. Incomplete Dominance Some alleles are neither dominant nor recessive In complete dominance, neither allele is dominant The heterozygous phenotype lies somewhere between the two homozygous phenotypes The heterozygous genotype yields a mixed phenotype

4. Codominance Phenotypes produced by both alleles are clearly expressed Many human genes are codominant, including blood types The heterozygous genotype yields BOTH phenotypes

5. Multiple Alleles Many genes exist in several different forms and are therefore said to have multiples alleles A genes that have more than two alleles is said to have multiple alleles An individual has only two copies of each gene, but more than two exist in a population EX: Rabbit fur color, human blood types

6. Polygenic Traits Many traits are produced by the interaction of several genes Traits controlled by two or more genes are said to be polygenic (many genes) traits Often show a wide range of phenotypes Four+ genes control human skin color

7. Genes and the Environment Environmental conditions can effect gene expression and influence genetically determined traits Phenotype is determined by genes + environment

8. Genes and the Environment Examples: Gene or Environment? – A blue eyed girl is born to two blue eyed parents – A pair of twins is separated at birth. They grow up in different countries and speak different languages. – A kitten is born with six toes.