Question

If a child has type \(\mathrm{O}\) blood and the mother is type A, then which of the following could be the blood type of the child's father? a. A only b. B only c. O only d. A or O e. A, B, or O

Short answer

The short answer is: The child's father could have blood type A, B, or O (answer choice e).

Step-by-step solution

Identify the genotypes of the mother and child

The mother has blood type A, which means her genotype could be either AA or AO. The child has blood type O, which means their genotype is OO.

Determine the possible genotypes of the father

To have a child with the genotype OO, one of the father's alleles must be O. The possible genotypes of the father would be AO, BO, or OO.

Match the father's genotypes with blood types

Using the genotypes we found above, we can determine the corresponding blood types. AO corresponds to blood type A, BO corresponds to blood type B, and OO corresponds to blood type O.

Choose the correct answer

Based on the possible blood types of the father, we can choose the correct answer, which is: e. A, B, or O

Key concepts

Genotype

In genetics, the term "genotype" refers to the genetic makeup of an organism. It's like the genetic blueprint that makes each individual unique at the DNA level. When discussing blood types, the genotype tells us which alleles are present in our genetic code that determine what blood group we belong to. Each person inherits two alleles for blood type, one from each parent. These alleles can combine in various ways to create different blood group expressions.

The human ABO blood type system consists of three alleles: A, B, and O. The presence of specific alleles produces the corresponding blood type. For instance, the genotype AA or AO results in blood type A, as the A allele is dominant. In the problem at hand, a mother with blood type A could have the genotype AA or AO. A child with blood type O must have the genotype OO, as this combination results in no antigen presence and is recessive.

Alleles

Alleles are different forms of a gene found at the same place on a chromosome and play a crucial role in inheritance. When we inherit traits, like our blood type, we get one allele from each parent. In the ABO blood group system, the alleles we talk about are A, B, and O, each contributing to the blood type expression.

In the exercise, to determine a child's blood type, we examine alleles received from both parents. Blood type O, which includes alleles of OO genotype, indicates that the child received an O allele from each parent. Thus, the father must carry at least one O allele to contribute towards the child's OO genotype. Understanding which alleles the father can contribute is crucial to solving the problem.

Blood Type A

Blood Type A is characterized by the presence of the A antigen on the surface of red blood cells. Its genotype can be either AA or AO. The A allele is dominant over the O allele, meaning that even if there's one A present, the blood type will exhibit as type A.

For the mother in the exercise, her blood type A could mean she either has the genotype AA, possessing two A alleles, or AO, containing one A and one O allele. This dominance of the A antigen is why a person with AO genotype still expresses blood type A. When solving problems like this one, knowing the possible genotypes behind a blood phenotype helps us determine parental contributions to the child's genotype.

Blood Type O

Blood Type O is unique because it lacks the presence of A or B antigens, giving it distinct characteristics among blood groups. The genotype for blood type O is OO, requiring that an individual inherit an O allele from each parent, making it recessive.

In the exercise, the child has blood type O, which means that both the mother and the father contributed an O allele. This allo... ws us to rule out phenotypes that do not have an accompanying O allele. The father's possible blood type could therefore be A, B, or O, provided one of these alleles is an O, as this would pair with the mother's contribution to result in the child's OO genotype. Understanding blood type O and its inheritance helps to clarify the range of potential parental contributions.