Polygenic inheritance
Definition
• Polygeny is when a single characteristic
may be controlled by more than one gene.
Several genes control the expression
of the same character
• These types of phenotype exhibit
continuous variation in a population.
– Eg skin colour, height
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
•
•
•
•
•
White - 0
Light - 1
Medium – 2
Dark – 3
Black – 4
• Complete the punnett square for a
heterozygous cross writing in the genotype
and phenotype.
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)
• What is the difference between continuous
and discontinuous variation?