Biology Inheritance / Variation & Genetics SZABMU 2024
PMDC Verified Question 4 of 94
In which type of dominance relationship phenotypic ratio is not same as genotypic ratio?
A
Complete dominance
B
Incomplete dominance
C
Over dominance
D
Codominance
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Complete dominance
Concept:

The relationship between alleles dictates how the underlying genotype translates into the visible phenotype.

Solution:

  • In Mendelian complete dominance, a monohybrid cross of heterozygotes (Aa x Aa) yields a genotypic ratio of 1:2:1 (1 AA : 2 Aa : 1 aa).
  • However, because the dominant allele completely masks the recessive one, both AA and Aa produce the exact same physical appearance. This creates a different phenotypic ratio of 3:1 (3 Dominant : 1 Recessive).
  • Therefore, the phenotypic ratio is not the same as the genotypic ratio.


Why other options are incorrect:

  • In Incomplete dominance and Codominance, the heterozygote (Aa) has a unique, distinct phenotype. Thus, both the genotypic and phenotypic ratios perfectly align at 1:2:1.

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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