1. Section 12.3 Complex Inheritance of Human Traits

2. Codominance Example in Blood
Sickle Cell - Homozygous Recessive
Normal RBC - Homozygous Dominant

3. Sickle Cell Anemia Cause
Heterozygotes are said to have sickle cell trait.
Defective Hemoglobin molecule (caused by 1 amino acid change) forms crystal-like structures that changes the shape of the RBC (sickle shape).

4. Blood Typing Lab Human Blood type exhibits Multiple Alleles.
Why Blood Type?
Incompatible blood types could cause Blood clotting and ultimately Death.
Use for Identification Purposes.
Paternity Tests (still require DNA testing)

5. Genetics Background Gene for Human Blood Type = Gene I
This gene codes for a molecule (antigen) that attaches to a membrane protein on the surface of RBCs.

6. Blood Antibodies

7. Polygenic Inheritance
Multiple genes are responsible for the phenotypes that we “see.”
Example:
Skin color (3 - 4 Genes)