1. Other Patterns of Inheritance

2. Learning Objectives  Describe examples of exceptions to Mendel’s principles.  Explain the relationship between genes and the environment.

3. Incomplete Dominance Some alleles are neither dominant nor recessive. Incomplete dominance: One allele is not completely dominant over another.

4. Codominance The phenotypes for both alleles are clearly expressed. Examples: chicken feather color, human protein controlling blood cholesterol levels

5. Multiple Alleles Many genes exist in more than two forms. Examples: human blood types, fur color in rabbits

6. Polygenic Traits Many traits are produced by the interaction of several genes. Examples: eye color in fruit flies, coat color in dogs Traits typically show a wide variety of phenotypes.

7. Non-Mendelian Inheritance Maternal inheritance: influences from DNA of maternal mitochondria and chloroplasts Genetic imprinting: chemical modification of certain genes

8. Genes and the Environment Environmental conditions can affect gene expression and influence genetically determined traits. The of an organism is only partly determined by its. phenotype genotype

9. Student Worksheet Answers