INCOMPLETE DOMINANCE, CODOMINANCE, MULTIPLE ALLELES, POLYGENIC TRAITS.
Incomplete Dominance & Codominance...Incomplete Dominance & Codominance Section 11-3 in Book. Review...
Transcript of Incomplete Dominance & Codominance...Incomplete Dominance & Codominance Section 11-3 in Book. Review...
Incomplete Dominance &
Codominance
Section 11-3 in Book
Review of Mendel’s Principles
Genes are passed parents
offspring; get one allele from each
parent
During Meiosis, the alleles for a gene
segregate from each other.
During Meiosis, genes independently
assort with each other.
Exceptions to Mendel’s principles
POLYGENIC TRAIT
Sometimes, a trait is controlled
by many genes
Ex. Hair color, eye color, skin
color, Height
Exceptions to Mendel’s principles
MULTIPLE ALLELES
Sometimes, a trait has more
than 2 versions of a gene
Blood Type (A,B, O)
A blending between two phenotypes.
(One allele not completely dominant over
the other.). (2 alleles produce 3
phenotypes.)
Result: Heterozygous phenotype
somewhere in between homozygous
phenotype.
Incomplete Dominance
1. Incomplete Dominance
Examples:
Trait: Flower Color
Expressions: Red x
White Pink
RR= Red; RW= pink; WW=
white
straight hair, wavy, curly
Incomplete Dominance
Both phenotypes are fully expressed when
present.
A cross between organisms with two
different phenotypes produces offspring
with has both phenotypes of the parental
traits shown.
Codominance
2. Codominance
Both alleles
contribute to the
phenotype.
Example: In
come chickens
Black Chicken x
White
Speckled
Chicken
YOU tell me which type of
dominance…
YOU tell me which type of
dominance…
Codominance!
Type of
Dominance?
Type of
Dominance?
Incomplete
Dominance!
A Trait found on the X chromosome
Males only need 1 copy of a recessive
allele to to express a sex-linked trait trait
Red Green Colorblindness
Sex-Linked Trait