ABO Blood Type Worksheet | PDF | Allele | Dominance (Genetics) - Free Printable

Here are the answers to the worksheet questions, worked out step by step.

1. Write the genotype for each person based on the description:

* a. Homozygous for the “B” allele:
"Homozygous" means having two of the same alleles. The allele for B is $I^B$.
Answer: $I^B I^B$

* b. Heterozygous for the “A” allele:
"Heterozygous" means having two different alleles. To have type A blood but be heterozygous, you must have one dominant A allele ($I^A$) and one recessive O allele ($i$).
Answer: $I^A i$

* c. Type O:
Looking at the chart, Type O corresponds to the genotype $ii$.
Answer: $ii$

* d. Type “A” and had a type “O” parent:
The person has Type A blood, so they have at least one $I^A$. Their parent was Type O ($ii$), meaning the parent could only pass down an $i$ allele. Therefore, the person received an $I^A$ from one parent and an $i$ from the other.
Answer: $I^A i$

* e. Type “AB”:
Looking at the chart, Type AB corresponds to the genotype $I^A I^B$.
Answer: $I^A I^B$

* f. Blood can be donated to anybody:
This describes the "Universal Donor." According to the chart, this is Type O.
Answer: $ii$

* g. Can only get blood from a type “O” donor:
If someone can *only* receive Type O blood, they cannot have A or B antigens themselves (otherwise they would react to O blood or be able to receive other types). This describes a person with Type O blood.
Answer: $ii$

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2. Pretend that Brad Pitt is homozygous for the type B allele, and Angelina Jolie is type “O.” What are all the possible blood types of their baby?

* Brad's Genotype: Homozygous Type B = $I^B I^B$
* Angelina's Genotype: Type O = $ii$

Let's do a quick cross (Punnett Square logic):
* Brad gives $I^B$ every time.
* Angelina gives $i$ every time.
* All babies will be $I^B i$.

Looking at the chart, the genotype $I^B i$ results in Type B blood.

Answer: Type B

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3. Draw a Punnett square showing all the possible blood types for the offspring produced by a type “O” mother and a Type “AB” father.

* Mother (Type O): $ii$
* Father (Type AB): $I^A I^B$

The Punnett Square:

| | $I^A$ (Father) | $I^B$ (Father) |
| :--- | :---: | :---: |
| $i$ (Mother) | $I^A i$ (Type A) | $I^B i$ (Type B) |
| $i$ (Mother) | $I^A i$ (Type A) | $I^B i$ (Type B) |

Possible Blood Types: Type A and Type B (50% chance for each).

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4. Mrs. Clink is type “A” and Mr. Clink is type “O.” They have three children named Matthew, Mark, and Luke. Mark is type “O,” Matthew is type “A,” and Luke is type “AB.” Based on this information:

* a. Mr. Clink must have the genotype:
Mr. Clink is Type O. There is only one genotype for Type O.
Answer: $ii$

* b. Mrs. Clink must have the genotype \_\_\_\_\_\_, because \_\_\_\_\_\_ has blood type \_\_\_\_\_\_.
Mrs. Clink is Type A ($I^A\_$). We need to figure out her second allele. They have a child, Mark, who is Type O ($ii$). For Mark to be $ii$, he must have gotten one $i$ from Dad and one $i$ from Mom. Therefore, Mom must carry the $i$ allele.
Answer: Mrs. Clink must have the genotype $I^A i$, because Mark has blood type O.

* c. Luke cannot be the child of these parents because neither parent has the allele \_\_\_\_\_\_.
Luke is Type AB ($I^A I^B$). He needs an $I^A$ allele and an $I^B$ allele.
Dad is $ii$ (no A or B).
Mom is $I^A i$ (has A, but no B).
Neither parent has the B allele to give to Luke.
Answer: B (or $I^B$)

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5. Two parents think their baby was switched at the hospital... The mother has blood type “O,” the father has blood type “AB,” and the baby has blood type “B.”

* a. Mother’s genotype:
Type O is always recessive.
Answer: $ii$

* b. Father’s genotype:
Type AB is codominant.
Answer: $I^A I^B$

* c. Baby’s genotype:
The baby is Type B. Since the mother is $ii$, she can only give an $i$. The father must have given the $I^B$. So the baby is heterozygous.
Answer: $I^B i$

* d. Punnett square showing all possible genotypes for children produced by this couple:

| | $I^A$ (Father) | $I^B$ (Father) |
| :--- | :---: | :---: |
| $i$ (Mother) | $I^A i$ (Type A) | $I^B i$ (Type B) |
| $i$ (Mother) | $I^A i$ (Type A) | $I^B i$ (Type B) |

*(Note: Since the baby in the problem is Type B, which appears in this square, the baby was likely NOT switched!)*

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Final Answer:

1.
a. $I^B I^B$
b. $I^A i$
c. $ii$
d. $I^A i$
e. $I^A I^B$
f. $ii$
g. $ii$

2. Type B

3.
Possible Offspring Genotypes: $I^A i$ and $I^B i$
Possible Offspring Phenotypes (Blood Types): Type A and Type B

4.
a. $ii$
b. $I^A i$; Mark; O
c. B (or $I^B$)

5.
a. $ii$
b. $I^A I^B$
c. $I^B i$
d. See the table in the explanation above (Offspring are 50% Type A and 50% Type B).