Incomplete Dominance & Codominance

1. Incomplete Dominance & Codominance

2. Review of Mendel’s Principles • Genes are passed parents  offspring; get one allele from each parent • The combination of alleles (genotype) determines the physical trait (Phenotype)

3. Exceptions to Mendel’s principles • Sometimes, there is no dominant or recessive gene, or the trait is controlled by many alleles or genes.

4. Incomplete Dominance • In Incomplete Dominance, one alleleisnotcompletely dominant over the other. Therefore the heterozygous phenotype results in a blending of the parental traits. • Result: Heterozygous phenotype somewhere in between dominant and recessive phenotypes.

5. 1. Incomplete Dominance Examples: • Trait: Flower Color Expressions: Red x White  Pink RR= Red; RW= pink; WW= white • straight hair, wavy, curly SS Ss ss

6. Incomplete Dominance

7. Codominance In codominance, neither allele are dominant; both are expressed. A cross between organisms with two different phenotypes produces offspring with has both phenotypes of the parental traits shown. 

8. 2. Codominance • Both alleles contribute to the phenotype. • Example: In some chickens Black Chicken x White  Speckled Chicken( not gray!)

9. YOU tell me which type of dominance… Codominance!

10. Type of Dominance? Incomplete Dominance!

11. Type of Dominance? Incomplete Dominance!