Multiple Alleles
Mr. and Mrs. Smith had a child with type A blood. At the same time and in the same
hospital, Mr. and Mrs. Rogers had a child with type O blood. A week after they took
their children home, the Smith's became concerned that their baby did not look like either
one of them. They returned to the hospital and had their blood types checked along with
the Rogers.
Smith's Blood Types
Mr. Smith: A
Mrs. Smith
0
Roger's Blood Types
Mr. Roger: O
Mrs. Roger: AB
a) Work out all possible Punnett squares.
b) If they were the only couples to have babies in the hospital at that time, do they
have the correct babies? Explain.
a) To work out all possible Punnett squares, we need to understand the inheritance patterns of blood types.
In humans, blood types are determined by multiple alleles at the ABO gene locus. The three alleles are usually referred to as A, B, and O.
Each individual inherits one allele from each parent. The A and B alleles are codominant, meaning that if both are present, both will be expressed. The O allele is recessive, meaning it will only be expressed if no A or B allele is present.
Let's construct the Punnett squares for the two couples:
Smith's Blood Types:
Mr. Smith: A (AA)
Mrs. Smith: 0 (OO)
Roger's Blood Types:
Mr. Roger: O (OO)
Mrs. Roger: AB (AB)
Punnett Square for Smith's Couple:
| A | A |
-----------------------------------
O | AO | AO |
-----------------------------------
O | AO | AO |
Punnett Square for Roger's Couple:
| A | B |
-----------------------------------
O | AO | BO |
-----------------------------------
O | AO | BO |
b) Based on the Punnett squares, we can see that both couples could have children with blood type A (AO) because both Mr. Smith and Mr. Rogers have the A allele. However, only the Smiths could have a child with blood type O (OO) because Mrs. Smith has the O allele and Mrs. Rogers has the AB allele.
Considering the blood types of the children, the Smiths' child has blood type A, matching the possible outcomes from their Punnett square. However, the Rogers' child has blood type O, which does not match the possible outcomes from their Punnett square. Therefore, the Rogers may not have the correct baby. It is possible that there was a mix-up or an error in the blood typing process. Further investigation is needed to determine the correct parentage.