Transcript Incomplete and Co-Dominance
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 Dominance If 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 (WW). These alleles show INCOMPLETE
DOMINANCE.
WHITE
chicken
B B What percent is black? White? Gray?
W BW BW Black: 0% White: 0% Gray: 100% W BW BW
Let’s Practice!
Cross a BLACK chicken (BB) with a (WW). These alleles show INCOMPLETE
DOMINANCE.
WHITE
chicken
B B What is the genotype and W phenotype of the F1 generation?
W BW BW BW BW Genotype: BW Phenotype: Gray
Let’s Practice!
What would the cross look like if you crossed two
GREY
chickens (BW). These alleles show
INCOMPLETE DOMINANCE.
B W What is the genotype and phenotype of the F2 generation?
B W BB BW BW WW Genotype: 1 BB 1 WW 2 BW Phenotype: 1 Black 1 White 2 Gray
Mrs. Smith and Ms. K’s Memory Trick
IN
complete is
IN
between
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 How many chickens in the F1 generation are completely black? White?
Black and white?
W W BW BW BW BW 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 What is the genotype and phenotype of the F1 generation?
W W BW BW BW BW Genotype: BW Phenotype: Black and white or checkered.
Let’s Practice!
Cross two Black and
White (c h e c k e r e
d) chickens (BW). These alleles show CO-DOMINANCE.
B W List all possible genotypes and phenotypes of the F2 generation.
B W BB BW BW WW Genotype: 1 BB 1 WW 2 BW Phenotype: 1 Black 1 White 2 Checkered
Mrs. Smith and Ms. K’s Memory Trick
CO
dominant alleles
CO