Biology Inheritance / Variation & Genetics KMU 2024
PMDC Verified Question 23 of 94
What is the primary outcome of crossing over during prophase of meiosis-I?
A
Chromosomes duplicate without any exchange of parts
B
Homologous chromosomes exchange different pairs leading to recombinant chromatids and increased genetic variation
C
Homologous chromosomes exchange identical parts, resulting in no genetic variation
D
Non-homologous chromosomes exchange parts
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Homologous chromosomes exchange different pairs leading to recombinant chromatids and increased genetic variation
Concept:

Crossing over is a highly precise physical exchange of DNA segments.

Solution:

  • During Prophase I, homologous chromosomes align closely (synapsis).
  • The primary outcome is that non-sister chromatids of these homologous chromosomes exchange segments.
  • This reciprocal exchange creates new allelic combinations, directly leading to recombinant chromatids and significantly increased genetic variation in the resulting gametes.


Why other options are incorrect:

  • Exchange of identical parts: This would defeat the purpose of the exchange; variation requires exchanging heterozygous differences.
  • Non-homologous chromosomes: Exchanging parts between different, non-homologous chromosomes is a harmful mutation called translocation, not natural crossing over.

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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