1. Co-dominance & Multiple Alleles Genetics of Blood

2. Human Blood Type One gene for blood type
Three different alleles (IA, IB, i)
IA and IB are co-dominant and ‘i’ is recessive
6 possible genotypes
4 possible phenotypes
Genotype
Phenotype
IAIA or IAi
Type A
IBIB or IBi
Type B
IAIB
Type AB ii
Type O

3. Percent of Population that has the O Blood Type by Region in the World

5. Co-dominance
Occurs when two different alleles for the same characteristic are fully expressed in the phenotype (e.g. Blood Type AB)
another example of co-dominance is in horses and shorthorn cattle where two alleles are expressed at the same time.
If one parent is homozygous red and the other is homozygous white, the offspring will be a pinkish colour termed “roan”, a blend of red and white. However, each individual hair in the coat is either completely white or completely red.

6. Practice Questions
1. Suppose a man with type AB blood and a woman with type O blood have a child. What are the possible blood types of the child? IA IB i
IAi
IBi
50% Type A
50% Type B

7. 2. Two parents have type AB blood
2. Two parents have type AB blood. What is the chance that they will have a child with type O blood? IA IB
IA IA
IAIB
IA IB
IBIB
There is a 0% chance that they will have a child with type O blood.

8. 3. Suppose a man has type B blood and a woman has type A blood
3. Suppose a man has type B blood and a woman has type A blood. Could they have a child with type O blood? IB i IA
IAIB
IAi
IBi ii
Yes, if both parents are heterozygous, it is possible for them to have a child with type O blood.

9. Blood Type Compatibility
Can Give Blood To
Can Receive Blood From A
A, AB
A, O B
B, AB
B, O O
A, B, AB, O AB
Type O is the universal donor
Type AB is the universal recipient

11. 4. Suppose that emergency surgery must be performed on a Type B patient during a blood shortage. The patient’s mother is type O, but cannot reach the hospital in time. Would blood from the patient’s father be suitable?
Possible father type 1
Possible father type 2 IA IB i
IAi
IBi
IA i IB i
IBi ii
IB i
The patient’s father could be type AB or type B. If the father is type B, he is a suitable donor. If the father is type AB, he is not a suitable donor.