Blood group which is not likely to be present in a baby born to mother with O positive and father with A nega… - RUHS, Jaipur, M.Sc Nursing Entrance Exam-2023

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2023

Pathology & Genetics

Hard

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2023

Explanation

The AB blood group requires the inheritance of both an A allele and a B allele.
The mother has blood type O, meaning her genotype is OO. She can only pass an O allele to her offspring.
The father has blood type A, meaning his genotype is either AA or AO. He can pass on an A or an O allele, but not a B allele.
Since neither parent possesses the B allele, it is genetically impossible for them to have a child with the AB blood group.

Option A: A positive is a possible blood group for the child. This occurs if the child inherits the A allele from the father, the O allele from the mother (genotype AO), and the Rh-positive allele from the mother.
Option B: A negative is a possible blood group. This occurs if the child inherits the A allele from the father, the O allele from the mother (genotype AO), and the Rh-negative allele from both parents (possible if the mother is heterozygous Rh+/-).
Option C: O positive is a possible blood group. This occurs if the father is heterozygous (AO) and passes on his O allele, the mother passes on her O allele (genotype OO), and the child inherits the Rh-positive allele from the mother.

Clinical Relevance

Nursing practice connection: Knowing The question tests the understanding of Mendelian inheritance of human blood groups, specifically the ABO and Rhesus (Rh) systems helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding blood group inheritance is crucial for genetic counseling and predicting the risk of blood group incompatibilities between a mother and fetus.
A key concern is Hemolytic Disease of the Fetus and Newborn (HDFN), which can occur when there is an incompatibility, most notably with the Rh factor (Rh-negative mother and Rh-positive fetus).
Knowledge of blood groups is fundamental for safe blood transfusions, ensuring that a recipient receives compatible blood to prevent life-threatening transfusion reactions.

How to Approach the Question

First, identify the core concept: genetic inheritance of blood types (ABO and Rh).
Determine the possible genotypes for each parent based on their given blood types (phenotypes). Mother (O positive) = OO, Rh status is +/+ or +/-. Father (A negative) = AA or AO, Rh status is -/-.
Systematically determine the possible alleles each parent can contribute to their child for both the ABO and Rh systems.
Use Punnett squares or list the combinations to find all possible genotypes and corresponding phenotypes (blood groups) for the offspring.
Compare the list of possible blood groups with the options provided in the question.
Select the option that does not appear in your list of possible outcomes.

Concept Tested & Keywords

Concept Tested: The question tests the understanding of Mendelian inheritance of human blood groups, specifically the ABO and Rhesus (Rh) systems.
Stem keywords: Blood group, baby, mother O positive, father A negative
Lead-in keywords: not likely to be present
Negative lead-in flag: The question asks for an outcome that is NOT possible.

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