Post on 25-Feb-2016
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Incomplete and Co-Dominance
Incomplete Dominance
• One allele is not completely dominant over the other.
• The heterozygous phenotype is in-between the homozygous phenotypes.
Incomplete DominanceIf you cross a RED flower with a WHITE flower, you will get a PINK flower.
NOTICE: the RED genotype is RR the WHITE genotype is WW the PINK genotype is RW
Let’s Practice!
Cross a BLACK chicken (BB) with a WHITE chicken (WW). These alleles show INCOMPLETE DOMINANCE.
B B
W
W
BW BW
BWBW
What percent is black? White? Gray?
Black: 0%White: 0%Gray: 100%
Let’s Practice!
Cross a BLACK chicken (BB) with a WHITE chicken (WW). These alleles show INCOMPLETE DOMINANCE.
B B
W
W
BW BW
BWBW
Genotype: BW
Phenotype: Gray
What is the genotype and phenotype of the F1 generation?
Let’s Practice!
What would the cross look like if you crossed two GREY chickens (BW). These alleles show INCOMPLETE DOMINANCE.
B W
B
W
BB BW
WWBW
Genotype: 1 BB 1 WW2 BW
Phenotype: 1 Black 1 White 2 Gray
What is the genotype and phenotype of the F2 generation?
Mrs. Smith and Ms. K’s Memory Trick
INcomplete is INbetween
Co-Dominance
• Both alleles contribute to the phenotype.
• For Example: In chickens, the allele for black feathers is co-dominant with the allele for white feathers. These chickens will have BOTH black and white feathers.
Let’s Practice!
Cross a Black chicken (BB) with a White chicken (WW). These alleles show CO-DOMINANCE.
B B
W
W
BW
BW
BW
BWHow many chickens in the F1 generation are completely black? White?Black and white?
Black: 0%White: 0%Both: 100%
Let’s Practice!
Cross a Black chicken (BB) with a White chicken (WW). These alleles show CO-DOMINANCE.
B B
W
W
BW
BW
BW
BWWhat is the genotype and phenotype of the F1 generation?
Genotype: BW
Phenotype: Black and white or checkered.
Let’s Practice!
Cross two Black and White (checkered) chickens (BW). These alleles show CO-DOMINANCE.
B W
W
B
WW
BW
BW
BBList all possible genotypes and phenotypes of the F2 generation.
Genotype: 1 BB1 WW2 BW
Phenotype: 1 Black1 White 2 Checkered
Mrs. Smith and Ms. K’s Memory Trick
COdominant allelesCOllaborate together
If you need more help…
READ PAGE 272