1. Exceptions to Mendelian Inheritance

2. Complete Dominance Mendel investigated complete dominance
dominant gene totally masks the recessive

3. Complete Dominance
Punnett squares are used to predict offspring genotypes and phenotypes.

4. Incomplete Dominance
A cross between organisms with two different phenotypes can produce offspring with a third phenotype that is a blending of the parental traits. 

5. Incomplete Dominance It's like mixing paints
Red + white will make pink
Red doesn't totally dominate the white, instead there is incomplete dominance, and we end up with something in-between.

6. Incomplete Dominance

7. Incomplete Dominance
How to recognize a question involving incomplete dominance:
Notice that the offspring show a 3rd phenotype.  The parents each have one, and the offspring are different from the parents.
Notice that the trait in the offspring is a blend of the parental traits.

8. Incomplete Dominance
Can still use the Punnett square to solve problems involving incomplete dominance. 
The letters used to represent each allele will be different, lowercase letters
Why lowercase?
Because neither allele dominates the other

9. r r Incomplete Dominance w w rw rw rw rw
r = red flowers w = white flowers
Cross red and white flowered plants
Results?
Genotype: 100% rw
Phenotype: 100% pink r r rw rw w rw rw w

10. bb x ww Incomplete Dominance
A cross between a blue bird & a white bird produces offspring that are silver. 
What are the genotypes of the parent birds in the cross?
b= blue
w= white
What is/are the genotype(s) of the silver offspring? bw
What would be the phenotypic percent of offspring produced by two silver birds?
25% blue
25% white
50% silver
bb x ww

11. ry x ry Incomplete Dominance
When two plants with orange fruits are crossed the following phenotypic ratios are present in the offspring: 25% red fruit, 50% orange fruit, 25% yellow fruit. 
What are the genotypes of the parent orange-fruited plants?
ry x ry

12. red x white = red & white spotted
Co-dominance
Prefix "co-" means "together“
Cooperate = work together
Coexist = exist together
The heterozygous organism has a third phenotype in which both of the parental traits appear together. 
red x white = red & white spotted

13. Co-dominance
A very very very very very common phenotype used in questions about co-dominance is roan fur in cattle. 
Cattle can be red, white or roan (red & white hairs together). 

14. Co-dominance Dominance

15. Co-dominance
Can still use the Punnett square to solve problems involving co-dominance. 
The letters used to represent each allele will be different, CAPITAL letters
RR = all red hairs
WW = all white hairs
RW = red & white hairs together.

16. Co-dominance How to recognize a question involving co-dominance:
Notice that the offspring show a 3rd phenotype.  The parents each have one, and the offspring are different from the parents.
Notice that in the offspring BOTH of the parental traits are expressed, not a mix.

17. Co-dominance
Predict the phenotypic ratios of offspring when a homozygous white cow is crossed with a roan bull.
50% WW - White
50% WR - Roan
What should the genotypes & phenotypes for parent cattle be if a farmer wanted only cattle with red fur?
Both parents should be RR, red

18. Co-dominance
A cross between a black cat & a tan cat produces a tabby pattern (black & tan fur together).
What pattern of inheritance does this illustrate?
Co-dominance
What percent of kittens would have tan fur if a tabby cat is crossed with a black cat?
0% tan
50 % Tabby
50% Black