Download Incomplete Dominance

Incomplete Dominance
Neither allele is dominant over the other
Heterozygous offspring have a phenotype
that is somewhere between the two.
 Red + White = ___________
Incomplete Dominance
Homozygous red parent: RR
crossed with
Homozygous white parent: WW
RR x WW
yields heterozygous offspring
RW that are pink
Incomplete Dominance
Codominance
 Both alleles contribute to the phenotype
 Heterozygous offspring express both alleles
X
Codominance: A black chicken crossed with a
white chicken results in a speckled chicken
How is this type of inheritance different from incomplete dominance?
Multiple Alleles
 > 2 possible alleles exist in a population
 Coat color in rabbits: at least 4 different
alleles
 C = full color (dominant other alleles)
 c (ch) = chinchilla
 c (h) = himalayan
 c = albino (recessive other alleles)
Full Color Rabbit (C)
Chinchilla Rabbit
partial defect in pigmentation: c (ch)
Himalayan Rabbit
Color in only certain parts of body: c (h)
Albino Rabbit (c)
Polygenic Traits
 Traits that are produced by the interaction of
more than one different genes
 Example: coat color in Labrador retrievers is
a result of interaction of 2 different genes.
Polygenic Inheritance
 2 or more genes work
together to create a
single phenotype
 Ex: Eye color, skin color
Polygenic Inheritance
 Example: comb shape in chickens is a
result of interaction between 2
different genes.
Epistasis
 When one gene product
affects the expression of
another gene.
 B, b = fur color alleles
 bb = brown fur
 Fur color only expressed
if C gene is also present