Question

a father and mother have four children. the childrens blood type are as follows:

• a son with type a blood
• a daughter with type b blood
• a daughter with type ab blood
• a son with type o blood

based on this information, what are the blood types of the parents? select all that apply.
□ a) the mother has heterozygous a blood.
□ b) the mother has homozygous o blood.
□ c) the father has heterozygous b blood.
□ d) the father has homozygous o blood.
□ e) the mother has homozygous a blood.
□ f) the father has homozygous b blood.

Explanation:

Step1: Recall Blood Type Genetics

Blood type is determined by alleles: \(I^A\), \(I^B\) (codominant), and \(i\) (recessive to \(I^A\) and \(I^B\)). Type O is \(ii\), type A is \(I^AI^A\) (homozygous) or \(I^Ai\) (heterozygous), type B is \(I^BI^B\) (homozygous) or \(I^Bi\) (heterozygous), type AB is \(I^AI^B\).

Step2: Analyze Child with Type O (\(ii\))

For a child to have \(ii\), both parents must contribute an \(i\) allele. So at least one parent has an \(i\) allele (heterozygous A, heterozygous B, or O).

Step3: Analyze Child with Type AB (\(I^AI^B\))

One parent contributes \(I^A\), the other \(I^B\).

Step4: Evaluate Options

• Option A: Mother heterozygous A (\(I^Ai\)): Can give \(I^A\) or \(i\). Possible.
• Option B: Mother homozygous O (\(ii\)): Can only give \(i\). But child with AB needs \(I^A\) and \(I^B\); mother can't give \(I^A\) or \(I^B\). Eliminate.
• Option C: Father heterozygous B (\(I^Bi\)): Can give \(I^B\) or \(i\). Possible (gives \(I^B\) for AB, \(i\) for O).
• Option D: Father homozygous O (\(ii\)): Can only give \(i\). Can't give \(I^B\) for AB. Eliminate.
• Option E: Mother homozygous A (\(I^AI^A\)): Can only give \(I^A\). Can't give \(i\) for O. Eliminate.
• Option F: Father homozygous B (\(I^BI^B\)): Can only give \(I^B\). Can't give \(i\) for O. Eliminate.

Answer:

A. The mother has heterozygous A blood.
C. The father has heterozygous B blood.