1. HW: Co-dominance Practice
Tuesday
April 4, 2017
I can:
predict offspring ratios for co-dominant traits
Agenda
(10) Catalyst
(25) GN and Board Work: Co-dominance and Blood Types
(40) Who’s the Daddy? Genetics
(10) Co-dominance Practice
Catalyst
How many phenotypes do you see in incomplete dominance? How does the heterozygote compare to the homozygotes?
Show all steps. Blue beetles and yellow beetles mate to produce green beetles. What is the likely outcome of a cross between a green beetle and a blue one?
HW: Co-dominance Practice

2. Exit Ticket Review B b B BB Bb b Bb bb
1. In mice, a certain species displays incomplete dominance in coat coloring. The offspring of a black (BB) mouse and a white (bb) mouse are gray (Bb) mice. A cross between two gray mice will most likely produce offspring with which percent of coat colors? A. 25% black, 75% gray B. 25% gray, 75% white C. 25% white, 25% black, 50% gray D. 25% gray, 25% black, 50% white
Draw a completed Punnett Square for the problem above. B b B BB Bb b Bb bb

3. Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.
complete dominance
incomplete dominance
co-dominance
multiple alleles
sex-linked

4. Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.

5. B = black W = white white black WW BB BW
Co-dominance is a pattern of inheritance in which both dominant alleles contribute to the phenotype. The heterozygous phenotype shows both traits.
When there are two dominant alleles in one genotype, both are expressed.
B = black
W = white
erminette (black AND white)
white
black WW BB BW

6. red cow + white cow = roan cow
(red and white)

7. ? BB black B = black W = white
Coat color in mice exhibits co-dominance. ? BB
black

8. ? WW white B = black W = white
Coat color in mice exhibits incomplete dominance. ? WW
white

9. ? BW checkered B = black W = white (black and white)
Coat color in mice exhibits co-dominance. ? BW
checkered
(black and white)

10. R = red
B = blue
Flowers exhibit co-dominance for petal color. ? RR
red

11. R = red
B = blue
Flowers exhibit co-dominance for petal color. ? BB
blue

12. ? RB red and blue R = red B = blue
Flowers exhibit co-dominance for petal color. ? RB
red and blue

13. R = red
W = white
Cow coat color follows a pattern of co-dominance. ? RR
red

14. R = red
W = white
Cow coat color follows a pattern of co-dominance. ? WW
white

15. R = red
W = white
Cow coat color follows a pattern of co-dominance. ? RW
roan

16. Solving a Co-dominance Problem
The two alleles for fish scale color, red and yellow, are co-dominant. If a red fish mates with a speckled red-and-yellow fish, what percentage of their offspring will be yellow?
Y = yellow; R = red
Solving a Co-dominance Problem R R
1. Read the problem. Underline the known alleles. Identify the type of inheritance as co-dominance. R R R R R
2. Choose a letter to represent each allele in the problem.
3. Circle and/or write down the genotypes of the parents. R R Y
4. Set up and solve Punnett Square. Y Y
5. Highlight and answer what the question is asking.
parents: RR x RY
yellow =
0/4 = 0%

17. What type of inheritance? (Complete, Incomplete, or Co-Dominance)
Red flowers are crossed with white flowers. All the flowers produced are red.
How do you know what type of inheritance it is?

18. What type of inheritance? (Complete, Incomplete, or Co-Dominance)
Red flowers are crossed with white flowers. All the flowers produced are pink.
How do you know what type of inheritance it is?

19. What type of inheritance? (Complete, Incomplete, or Co-Dominance)
Red flowers are crossed with white flowers. All the flowers produced are speckled red-and-white.
How do you know what type of inheritance it is?

20. What type of inheritance? (Complete, Incomplete, or Co-Dominance)
A black cat mates with a white cat. All of their children are white with black spots.
How do you know what type of inheritance it is?

21. What type of inheritance? (Complete, Incomplete, or Co-Dominance)
A red flower is crossed with a yellow flower. All of the flowers produced are orange.
How do you know what type of inheritance it is?

22. What type of inheritance? (Complete, Incomplete, or Co-Dominance)
A red flower is crossed with a yellow flower. All of the flowers produced are red-and-yellow.
How do you know what type of inheritance it is?

23. An important example of co-dominance AND multiple alleles is human blood groups.
The proteins on the surface of red blood cells determine your blood type, and those are determined by genes.
both A and B proteins are expressed = codominance!

24. IA = type A (dominant) IB = type B (dominant) i = type O (recessive)
Human blood type is determined by 3 alleles (2 dominant, 1 recessive):
Just like with any other trait, you must have two alleles for blood type. You still inherit one allele from each parent.
IA =
type A (dominant)
IB =
type B (dominant)
i =
type O (recessive)
phenotypes:
IAIA or IAi
IBIB or IBi
IAIB ii
genotypes:

25. What’s the blood type? ii
type O

26. What’s the blood type?
IAi
type A

27. What’s the blood type?
IAIB
type AB

28. What’s the blood type?
IBIB
type B

29. What’s the blood type?
IAIA
type A

30. What’s the blood type?
IBi
type B

31. Write the genotype for the phenotype described:
heterozygous type A
IAi

32. Write the genotype for the phenotype described:
homozygous type B
IBIB

33. Write the genotype for the phenotype described:
homozygous type A
IAIA

34. Write the genotype for the phenotype described:
heterozygous type B
IBi

35. Write the genotype for the phenotype described:
type O ii

36. Write the genotype for the phenotype described:
type AB
IAIB

37. Write the genotype(s) for the phenotype described:
type A
IAIA or IAi

38. Write the genotype(s) for the phenotype described:
type B
IBIB or IBi

39. Solving Blood Type Problems
A woman who is heterozygous for blood type B has a child with a man with heterozygous type A blood. What are the possible genotypes of their children?