Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
BEYOND MENDEL’S LAWS
Mendel studied traits that were purely dominant or recessive. Unfortunately, in nature, there exists more than simply two choices for some traits.
Snapdragons can be white, red, pink, yellow, or orange.
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
INCOMPLETE DOMINANCE
Neither trait is dominant or recessive. A heterozygous individual is a blend of the two traits.
Ex. Snapdragons
Instead of using uppercase and lowercase R and r, we use subscripts to show incomplete dominance of a trait. For example FR (red flowers) and FW (white flowers).
Red = FR FR
Pink = FR FW White = FW FW
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
INCOMPLETE DOMINANCE
Cross a Red Flower with a White flower:
Cross two plants from the F1:
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
CO­DOMINANCE
BOTH alleles for a trait are dominant, a heterozygous individual expresses both traits.
Ex. Black rooster FBFB x white hen FWFW. The F1 are all ‘barred’ (FBFw black and white feathers)
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
MULTIPLE ALLELES
Human blood types are an example of a gene that has multiple alleles (as well as co­
dominance). Alleles include IA, IB, and i.
IA and IB are co­dominant with each other and both are dominant over i.
Together they make 4 different blood types.
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
MULTIPLE ALLELES
What are the genotypes for the four possible human blood types?
Type A
Type B
Type AB
Type O
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
EXAMPLE
In four o’clock plants, red flowers are incompletely dominant over white flowers. Heterozygous flowers are pink. If a red flower is crossed with a white flower what is the colour of:
The F1 generation?
The F1 generation crossed with the red parent?
The F1 generation crossed with the white parent?
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
EXAMPLE
A cross between a yellow snake & a blue snake produces offspring that are all green: What are the genotypes of the parent generation (P)? What are the genotypes of the F1 generation? What would be the phenotypic ratios of offspring produced by two green snakes?
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
EXAMPLE
If a woman has AB blood, and a man has type A blood, what are the possible blood types of their offspring?
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Day 06 inc and codominance and multiple alleles filled in.notebook
February 12, 2013
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