Simple Inheritance:
Complex Inheritance:
What does the word “simple” mean?
(student example)
What does the word “complex” mean?
(student example)
Simple inheritance:
When there are only two alleles and one gene for a trait and
one allele is dominant.
The dominant allele is what we see in the phenotype
Complex inheritance:
When traits are determined by more factors. What you see in
the phenotype is based on more complex arrangements.
1. Codominance
2. Incomplete dominance
3. Multiple alleles
4. Sex-linked
5. Environment
6. Polygenic
Examples:
Pea plant flower color: purple (P) or white (p)
(student example)
Traits more complex:Some traits are even more complex and show patterns of
more than one of the complex traits:
1. Blood type:
 A or B are Codomiant
 O is recessive to both
 A, B and O are an example of multiple alleles
2. Cat fur color:
 Multiple alleles fur shade of black, brown or
cinnamon.
 Polygenic – at least six genes work together
 Environment – for Siamese cats
3. Eye color in humans:
 Simple: Brown vs. blue
 Polygenic – green eyes adds another gene.
Final note: They will need to know the “definitions” of simple vs. complex inheritance for the quiz and I will have it on the
crossword.