Question

The genotype of a husband and wife are I^AI^B & I^AI^O. Among the blood types of their children, how many different genotypes & phenotypes are possible?

• A. 3 genotypes; 3 phenotypes
• B. 4 genotypes; 3 phenotypes
• C. 4 phenotypes; 3 genotypes
• D. 4 phenotypes; 4 genotypes

Answer 1

The Correct Option is B

We are given the genotypes of the husband and wife for the ABO blood group system:

• Husband's genotype: I^AI^B (Blood type AB) 
• Wife's genotype: I^AI^O (or I^Ai) (Blood type A)

The ABO blood group system involves three alleles: I^A, I^B, and I^O (or i). I^A and I^B are codominant, and both are dominant over I^O.

1. Determine the possible gametes produced by each parent:

• Husband (I^AI^B) can produce gametes containing either the I^A allele or the I^B allele.
• Wife (I^AI^O) can produce gametes containing either the I^A allele or the I^O allele.

2. Use a Punnett square to find the possible genotypes of the children:

	Wife's Gametes
Husband's Gametes	IA	IO
IA	IAIA	IAIO
IB	IAIB	IBIO

3. List the possible genotypes of the children:

• I^AI^A
• I^AI^O
• I^AI^B
• I^BI^O

All four genotypes are distinct. Therefore, there are 4 different possible genotypes.

4. Determine the phenotype (blood type) for each genotype:

• I^AI^A → Blood type A
• I^AI^O → Blood type A (I^A is dominant over I^O)
• I^AI^B → Blood type AB (I^A and I^B are codominant)
• I^BI^O → Blood type B (I^B is dominant over I^O)

5. List the possible phenotypes of the children:

• Blood type A
• Blood type AB
• Blood type B

Even though there are four possible genotypes, two of them (I^AI^A and I^AI^O) result in the same phenotype (Blood type A). The distinct phenotypes are A, AB, and B. Therefore, there are 3 different possible phenotypes.

Conclusion: There are 4 different genotypes and 3 different phenotypes possible among the children.

Comparing this with the options: The correct option is 4 genotypes; 3 phenotypes.

Answer 2

Given the genotypes:

Husband: IAIB (Blood group AB)
Wife: IAi (Blood group A)

Let’s perform a cross to determine the possible genotypes and phenotypes of their children.

	IA (wife)	i (wife)
IA (husband)	IAIA	IAi
IB (husband)	IAIB	IBi

Possible Genotypes:

1. IAIA
2. IAi
3. IAIB
4. IBi

Possible Phenotypes:

1. Blood group A (from IAIA and IAi)
2. Blood group AB (from IAIB)
3. Blood group B (from IBi)

Thus, the correct answer is (B) : 4 genotypes; 3 phenotypes.