Post on 10-Jun-2020
CODOMINANCE AND INCOMEPLETE DOMINANCE
3/13/18
PAGE 98DO NOW ‣ The trait is a sex-linked recessive trait. Fill in
the genotypes of all individuals.
AGENDA▸ Codominance
▸ Incomplete dominance
▸ Punnett Square
SPECIAL CASES OF DOMINANCE
CORNELL NOTES TITLE (PAGE 99)
PAGE 99
GENERATIONS▸ P - parents
▸ F1 - offspring of parent generation
▸ F2 - offspring of offspring
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SPECIAL CASES OF DOMINANCE▸ Incomplete dominance
▸ Co-dominance
WHAT THE HECK?• Red (RR) + White (rr) produces all Rr offspring
• Rr is suppose to be RED!
• But when the words INCOMPLETE DOMINANCE are there, ONLY THEN will it be a mix between red and white = PINK.
R R
r Rr Rr
r Rr Rr
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INCOMPLETE DOMINANCE▸ When dominant and recessive traits MIX/
BLEND to create an in-between trait
▸ Can only happen in HETEROZYGOUS genotype (Aa)
▸ Example: Red (AA) + White (aa) = Pink (Aa)
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INCOMPLETE DOMINANCE PUNNETT SQUARE▸ R = red (incomplete dominance), r = white
▸ Rr x rr
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EXAMPLE 1▸ B=blue flowers (incomplete dominance),
b=yellow flowers
▸ Bb x Bb
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EXAMPLE 2▸ B=blue flowers (incomplete dominance),
b=yellow flowers
▸ Green flower x yellow flower
MORE EXAMPLES OF INCOMPLETE DOMINANCE
WHAT DOES CO- MEAN?• Co-captain (2 captains)
• Co-leader (2 leaders)
• Co-Ed (both boys and girls in a school)
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CODOMINANCE▸When both alleles are dominant.
▸ Sometimes there is no recessive allele
▸ BOTH traits show up in phenotype
▸ Traits DON’T BLEND.
Example: Pink and White alleles both expressed. NO BLENDING.
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CO-DOMINANCE PUNNETT SQUARE▸ Use two different capital letters to signify that
both alleles are dominant
▸ B = black, W = white
▸ BB x WW
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EXAMPLE 3▸White coat color and black coat color are
codominant in chicken.
▸ BW x BW
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EXAMPLE 4▸ Pink and white petals are both dominant in a
type of flower
▸ Cross a pink flower with a white flower
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NOTE▸ Sometimes, some problems will use these
alleles for co-dominance:
▸ B = black, B’ = white
▸ BB x BB’
MORE EXAMPLES OF CO-DOMINANCE
BLOOD TYPE CODOMINANCE
The blood type gene has 3 possible alleles:
IA, IB, and i (i = O type blood)
Every person gets two of those alleles (1 from mom and 1 from dad)
IA and IB are CODOMINANT while i is recessive.
IAIA or IAi = Type A bloodIBIB or IB i = Type B bloodIAIB = Type AB blood (codominant)i i = Type O blood (homozygous recessive!)
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INCOMPLETE DOMINANCE VS. CODOMINANCE▸ Incomplete
▸ Blending traits
▸ Codominance
▸ BOTH traits appear
PRACTICE• Work on the “Co-Dominance/
Incomplete Dominance worksheet”
• Glue this to your Practice notebook when finished
ILLUSTRATIVE SUMMARYPAGE 98 -AT LEAST 4 COLORS -MUST INCLUDE ALL CONCEPTS -LABEL APPROPRIATELY
EXIT SLIP• Take out a half sheet of paper
EXIT SLIPCOPY THE QUESTIONS
1. Blue flowers (B) is incompletely dominant over yellow flowers (b). Cross a green flower and a yellow flower and list all the genotypes and phenotype probabilities of the offspring
2. What is the genotype of this dog? If this dog is crossed with another spotted dog, what will be the genotypes and phenotypes of the offspring? (use percentages)