1. Bellwork: Thurs. Jan. 18, 2018
Dihybrid: 2-Factor Cross: First Generation: F1  
Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy):
Cross: RRYY x rryy
(R) = Round seeds (r) = wrinkled seeds
(Y) = Yellow seeds (y) = green seeds
Genotypic Ratio: ______________
Phenotypic Ratio: ______________

2. https://www. youtube. com/watch

3. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall

4. Incomplete & Codominance

5. Incomplete Dominance: when one allele is not completely dominant over another. The heterozygous phenotype is a “mix of the two homozygous phenotypes.
A cross between red (RR) and white (WW) four o’clock plants produces pink-colored flowers (RW).

7. Incomplete dominance – when one allele is not completely dominant over the other allele
WW = White
RR = Red WW X RR
RW = Pink
Genotypic Ratio:__________
Phenotypic Ratio:_________

8. What happens if you cross the offspring (F1) generation?
RW x RW
Genotypic ratio
Phenotypic Ratio
Phenotypic Ratio:
Genotyopic Ratio:

9. Codominance
Is a lot like incomplete dominance - A hybrid organism shows a third phenotype --- not the usual dominant versus recessive traits. BUT in codominance both traits show up AT THE SAME TIME!!

10. Co-dominance: when both alleles contribute to the phenotype.
A cross of black chicken (BB) with a white chicken (WW) produces all speckled offspring (BW). BB = black feathers
BW = black and white feathers
WW = white feathers
Genotypic Ratio:
Phenotypic Ratio:

11. Or…. Roan coat color in horses and cows.

12. Co-dominance: Roan fur. Cattle can be
red (RR = all red hairs),
white (rr = all white hairs), or
roan (Rr = red & white hairs together). 
Notice how this cross looks just like the others we have done earlier with dominant and recessive alleles – I would have to tell you this is a co-dominant cross!!!.
Cross: ______ X _______
Genotypic Ratio:_____________
Phenotypic Ratio:____________

13. Now let’s cross two roans:
Cross:_____ X______
Genotypic Ratio:
Phenotypic Ratio:

14. roan horses

16. Copyright Pearson Prentice Hall
End
Copyright Pearson Prentice Hall

17. The Punnett square predicts a Genotypic Ratio: 1:1:2:2:4:2:2:1:1
Phenotypic Ratio:
9:3:3:1
When Mendel crossed plants that were heterozygous dominant for round yellow peas, he found that the alleles segregated independently to produce the F2 generation.
F2 Represents:
Independent Assortment

18. Bellwork: Mon???. Jan. 20??, 201?
Dihybrid: 2-Factor Cross: First Generation: F1  
Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy):
Cross: RRYY x rryy
(R) = Round seeds (r) = wrinkled seeds
(Y) = Yellow seeds (y) = green seeds
Genotypic Ratio: ______________
Phenotypic Ratio: ______________

19. Bellwork: Mon. Jan. 9, 2012 RRYY x rryy
Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy):
Set up the Punnet Square for this cross:
RRYY x rryy