1. Non-Mendelian Inheritance

2. Not all traits exhibit simple dominant and recessive expression.
Incomplete Dominance
Multiple Alleles
Codominance
Polygenic Traits
Environmental Effects

3. Incomplete Dominance
Incomplete dominance – heterozygous phenotype is intermediate between that of either homozygote
Produces a blended phenotype

4. Incomplete Dominance
A man with straight hair mates with a woman that has curly hair what is the chance of their offspring having wavy hair?
Dad HH
Mom hh x H H HH
Straight h Hh Hh Hh
Wavy h Hh Hh hh
Curly
100% Wavy

5. Codominance
Codominance - both alleles are expressed at the same time in the heterozygote
Ex: Rhone horse
Has both black
and white hairs

6. Example: Problem
You breed a white chicken with an Andalusian blue rooster (black and white feathers). What are the potential offspring?
Dad BW
Mom WW x B W BB
Black W BW WW BW
Andalusian W BW WW WW
White
50% Andelusian; 50% White

7. Multiple Alleles More than 2 alleles control trait.
Diploid organism can only have 2 alleles.
Example: Rabbit fur color
C (wildtype), ch (himalayan), cch (chinchilla), c (albino)
wildtype
himalayan
chinchilla
albino

8. Multiple Alleles Human Blood Type 3 alleles -- IA , IB , and IO
IA and IB are codominant
IO is recessive
Type A blood can be IAIA or IAIO
Type B blood can be IBIB or IBIO
Type AB blood is IAIB - codominant state
Type O blood is IOIO

9. Blood type
A woman with AB blood type has a baby with B blood type. Is it possible for a man with type A blood to be the father? If so what is the mans genotype?
Dad
IA -
Mom
IAIB x
Type A blood can be IAIA or IAIO
Type B blood can be IBIB or IBIO
Type AB blood is IAIB - codominant state
Type O blood is IOIO IA - IA
IAIA
IA- IB
IAIB
IB-
Yes
Dad must be IAIO

10. Polygenic Inheritance
Wide range (continuum) of phenotypes
Human skin color
Height and weight
Two or more genes responsible for trait.

11. Polygenic Inheritance Skin Color

12. Environmental effects
Color resembles snowy background in winter
The expression of some genes is influenced by environmental factors, such as temperature
Some alleles are
heat-sensitive
Arctic foxes, cats, rabbits make fur pigment only when the weather is warm
Color resembles tundra background in summer