1. CoDominance and Multiple Alleles
Patterns of Inheritance
CoDominance and Multiple Alleles

2. Co Dominance:
The “recessive” and “dominant” traits appear together in the phenotype of hybrid organisms
Think “co-” is together (cooperate, coexist)
Red x White  Red & White Spotted

3. EXAMPLES:

4. Multiple Alleles:
A condition in which more than two alleles exist for a given trait.
EXAMPLES: Blood Types, Eye color, Skin color, Hair Color

5. Eye Color Alleles
Eye color is controlled by several pairs of melanin-producing genes, and as a result, human eyes come in a range of shades of blue and brown, as well as green, gray, and hazel.

6. Skin Color Alleles
In skin color, for example there are several pairs of genes that code for the pigment melanin. The more copies of the dominant allele a person has, the darker their skin.

7. Blood Types There are 3 different alleles for blood type, (A, B, & O)
A is dominant to O
B is also dominant to O
A and B are both codominant

8. Blood Transfusions
Blood can only be transferred to a body of a person who's immune system will "recognize" it.
Type A = A antigens
Type B = B antigens
Type O = No antigens
O is the universal donor
a person can receive a transfusion from O blood without having an immune response
AB is the universal recipient
because a person with AB blood has both the A and B antigens already in the body

9. Blood Typing

10. In humans, there are four types of blood; type A, type B, type AB, and type O. The alleles A and B are codominant to each other and the O allele is recessive to both A and B alleles.
So a person with the genotype AA or AO will have A type of blood.
a. What possible genotypes will produce B type of blood? ________________________
b. What is the only genotype that will produce O type of blood?____________________
c. What is the only genotype that will produce AB type of blood?___________________

11. Practice Problems:
1. You are blood type O and you marry a person with blood type AB.
a. Complete a Punnett square for this cross. Include Genotypes and Phenotypes.

12. Give the genotype and phenotypes of all six individuals.
2. In a family represented by this pedigree, the blood types of the parents are different.
Each of the four children has a blood type that is different from the other children.
Give the genotype and phenotypes of all six individuals.    m f m f f m