2. Beyond Mendel
Mendel discovered that in some traits, one allele is dominant over the other allele (we call this simple dominance)
However, many traits do not work like that
Ex.
Incomplete dominance
Codominance

3. Incomplete Dominance Neither trait is dominant or recessive
A heterozygous individual will have a blend of the two traits
Ex. Snapdragons
Instead of using R and r, we use
FR and FW to show incomplete
dominance
Red = FR FR
Pink = FR FW
White = FW FW

4. Incomplete dominance example
Cross a red flower with a white flower:
If we crossed two plants from the F1 generation, we would get:

5. Co-dominance BOTH alleles for a trait are dominant
A heterozygous individual expresses both traits
Ex. Black rooster breeds with a white hen
Black: FBFB
White: FWFW
The F1 are all “barred”
(black and white feathers)

6. Example
In four o’clock plants, red flowers are incompletely dominant over white flowers.
Heterozygous flowers are pink.
If a red flower is crossed with a white flower, what is the colour of:
The F1 generation?
The F1 generation crossed with the red parent?
The F1 generation crossed with the white parent?

7. Example 2
A cross between a yellow snake & a blue snake produces offspring that are all green: 
What are the genotypes of the parent generation (P)?
What are the genotypes of the F1 generation?
What would be the phenotypic ratios of offspring produced by two green snakes?

8. Sickle cell anemia
An inherited genetic condition that results in a decrease in the ability of red blood cells to carry oxygen
Sickle red blood cells become hard and irregularly shaped
Become clogged in blood vessels
Causes excruciating pain, damage to body organs and even death

9. Sickle cell anemia
If you are a carrier of sickle cell anemia, you have higher resistance to malaria – a deadly disease caused by a protist, common in warm areas
Sickle cell carriers have a survival advantage compared to those who do not
Therefore, the allele for sickle cell is passed on more frequently

10. Polygenic inheritance
Some traits are a result of a combination of many genes
Ex. Height, skin colour, eye colour
Depending on which alleles you inherit for each of these genes, your traits may fall inside a great range

11. Polygenic inheritance

12. Polygenic inheritance