1. Polygenic inheritance

2. Definition
Polygeny is when a single characteristic may be controlled by more than one gene.
Several genes control the expression
of the same character

3. These types of phenotype exhibit continuous variation in a population.
Eg skin colour, height

4. Skin colour 5 possible phenotypes 9 genotypes
Melanin production is controlled by 2 genes
The amount is directly proportional to the number of dominant alleles

5. White - 0
Light - 1
Medium – 2
Dark – 3
Black – 4
Complete the punnett square for a heterozygous cross writing in the genotype and phenotype.

6. Activities
Determine the phenotypes of the offspring for the following:
A mating of white with black
A mating between two individuals of medium skin colour
If 5 phenotypes are possible for two genes, how many are possible for three (eg A, B and C)

7. What is the difference between continuous and discontinuous variation?