1. 10.3 Variations of Inheritance Pg 215-217

2. Codominance 1 gene with 2 allele variations 3 phenotypes ( outward appearance) Genotypes are written with capital letters and superscripts – same as in intermediate inheritance problems. Designations. Co= together- see both parent alleles. Examples- –roan cattle- C R C W = red and white hair –Tabby cat Black and tan fur –AB blood type- both A and B antigens on the red blood cells. Do Codominance problems 1-3 Do Sneech Handout

3. Multiple Alleles 1 gene but more than 3 alleles Results in more genotypes and more phenotypes. More variations in species. Best example is ABO blood group –3 alleles- IA, I B, i 6 genotypes 4 phenotypes (blood groups)

4. ABO Blood Groups- Blood Type AB= Codominant

5. Polygenic Inheritance 2 or more genes affect a single characteristic Even more genotypes and phenotypes. Human traits- hair color, eye color, height, skin color. –3 genes for height= 6 alleles

6. Environmental Effects Phenotype depends on the environment. Environment does not affect the genotype just the expression. Examples- –Temperature, nutrition, exercise, exposure to sunlight –Identical twin studies. –Most human traits are a combination of genes and environment.