Download Incomplete dominance and Codominance Note

Incomplete Dominance Inheritance
Beyond Mendel's Observations
Scientists now realize that patterns of inheritance are more complicated than
Mendel proposed.
Therefore, the possible alleles for the trait "rose colour" are ...
W
F - this is the allele for the gene to produce white pigment
R F
this is the allele for the gene to produce red pigment
Incomplete Dominance
The following genotypes and corresponding phenotypes are possible:
Genotype
Example:
For a specific species of rose, if a red flowered rose plant is crossed with a
white flowered rose, the offspring will all produce pink roses.
Phenotype
FF
FF
FF
W
W
R
R
W
R
The ratios of the offspring are 1 red, 2 pink, and 1 white.
Incomplete Dominant Alleles are symbolized by a
(i.e.
Fw )
and a
Incomplete Dominance Inheritance
Incomplete Dominance Inheritance
ex 1: Cross a white rose with a red rose that
show incomplete dominance
Genotypes:
F is the allele for the gene to produce white pigment.
F is the allele for the gene to produce red pigment.
W
R
Parents:
Phenotypes:
Genotypic Ratio
Phenotypic Ratio
Incomplete Dominance Inheritance
Incomplete Dominance Inheritance
ex 2: Cross a pink rose with a pink rose that
show incomplete dominance
F
F
W
R
Genotypes:
is the allele for the gene to produce white pigment.
is the allele for the gene to produce red pigment.
Phenotypes:
Parents:
Genotypic Ratio
Incomplete Dominance Inheritance
Phenotypic Ratio
Codominant Alleles
Two alleles that are
. This means that the
phenotype clearly shows both variations of that trait (it is NOT a blended trait).
a) Codominant alleles are symbolized by a
with a
b) Codominant alleles express
allele phenotypes.
c) The presence of both phenotypes is commonly referred to as "
"
LCLC
T T
LL
LT LC
Codominance Inheritance
Sickle Cell Anemia is one of the most thoroughly studied
genetic disorders.
- normal red blood cells are flat and disk-shaped
- sickle-shaped cells are elongated and C shaped
- misshaped red blood cells do not transport
oxygen effectively because they cannot pass
through small blood vessels.
- this leads to blockages and tissue damage
ex 3: Cross a red cow with a white cow that shows
co-dominance
C W is the allele for the gene to produce white pigment.
C R is the allele for the gene to produce red pigment.
Parents:
HbAHbA HbAHbS HbSHbS -
An individual being heterozygous with the the sickle cell
trait are resistant to malaria. In certain parts of Africa this
could be an advantage.
Co-dominance Inheritance
Genotypes:
Phenotypes:
ex 3: Cross a roan cow with a roan cow
C W is the allele for the gene to produce white pigment.
C R is the allele for the gene to produce red pigment.
Parents:
Genotypic Ratio
Phenotypic Ratio
Co-dominance Inheritance
Genotypes:
Phenotypes:
Genotypic Ratio
Phenotypic Ratio