Download CoDominance Worksheet

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This worksheet gives you practice in problems dealing with incomplete dominance. Below is a complete
example for you to follow.
Important information: Codominant traits are different from simple dominant traits because
heterozygous individuals can have multiple dominant alleles. This results in both traits being
expressed simultaneously. There is also a recessive trait that can be present.
EXAMPLE:
Blood type:
Type A: IAIA or heterozygous A: IAi
Type B: IBIB or heterozygous B: IBi
Type AB: IAIB
Type O: ii
Note: IA denotes that the allele is a dominant allele form "A". The "A" protein will be made on the red blood cells.
IB denotes that the allele is a dominant allele form "B".
The "B" protein will be made on the red blood cells
IA IB denotes that the individual has both forms of dominant alleles "A" and "B". Both proteins made.
ii denotes that the individual has both recessive alleles. No proteins made on red blood cell.
Parent A: Heterozygous A
Parent B: Homozygous B
Calculate the probability of each phenotype being passed down to the offspring.
INFORMATION:
I
A
i
I
B
IAIB
IB i
I
B
IAIB
IB i
Notice how the punnett square is set up so that one
parent has the genotype across the top.
The other parent's genotype is down the side.
The table is filled in according to the corresponding
genotype.
TOTALS:
A: 0 out of 4…….0/4
B: 2 out of 4……..2/4
AB: 2 out of 4……2/4
O: 0 out of 4…….0/4
If the question asks for a ratio, you must do the following:
-Use the total for that phenotype.
-Write the ratio with a labeled number.
Ratio for above problem: 0: 2:2:0
Ratio for above problem: 0A: 2B : 2AB : 0 O
Practice:
1.) Heterozygous A crosses with Heterozygous A.
Calculate the probability of each phenotype being passed down to the offspring.
TOTALS: (percent and ratio)
A:
B:
AB:
O:
2.) Type O breeds with Type AB
TOTALS: (percent and ratio)
A:
B:
AB:
O:
3.) Woman has type B (exact genotype unknown). Man has type O. What are the possible blood types of
their kids?
Is this type possible:
A:
yes/ no?
B:
yes/ no?
AB: yes/ no?
O:
yes/ no?
3B.) If the woman has a baby with type AB blood, could the man above be the father? Explain you answer.