Biology Inheritance / Variation & Genetics BUMHS 2022
PMDC Verified Question 60 of 94
How many phenotypes are possible for human ABO blood group system?
A
2
B
4
C
6
D
8
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 4
Concept:

A phenotype is the observable expression of a genetic trait.

Solution:

  • The human ABO blood group system is controlled by three alleles (\(I^A\), \(I^B\), \(i\)).
  • While these alleles interact to form six possible genotypes (\(I^A I^A\), \(I^A i\), \(I^B I^B\), \(I^B i\), \(I^A I^B\), \(ii\)), they manifest physically as only four phenotypes.
  • The four phenotypes are: Type A, Type B, Type AB, and Type O.


Why other options are incorrect:

  • 6: Refers to the number of genotypes, not phenotypes.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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