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Difficulty: MediumKingdom Protista: Protozoa and Unicellular Algae

A microscopic examination of *Paramecium caudatum* reveals two distinct nuclei within the cell: a larger macronucleus and a smaller micronucleus. If an experimental procedure destroys the micronucleus while keeping the macronucleus fully functional, which biological process will the organism be unable to undergo?

  1. Sexual reproduction and genetic recombination through conjugationAnswer
  2. B
    Oxygen production via the photolysis of water during light-dependent reactions
  3. C
    Extracellular breakdown of organic matter through saprophytic digestion
  4. D
    Maintenance of an acellular nucleoprotein structure lacking a membrane

Answer

Sexual reproduction and genetic recombination through conjugation
In ciliates like Paramecium, nuclear dualism divides cellular duties: the macronucleus governs somatic metabolic processes and vegetative division, while the micronucleus is essential for meiotic division, sexual reproduction, and genetic recombination during conjugation. Destruction of the micronucleus specifically prevents conjugation and genetic exchange.

Step-by-Step Solution

1
Identify the functional roles of the two nuclei (nuclear dualism) in Paramecium.
The macronucleus regulates day-to-day metabolic activities and vegetative growth, whereas the micronucleus stores the germline genome.
Protozoans in the class Ciliophora exhibit nuclear dualism separating metabolic control from reproductive inheritance.
2
Evaluate the effect of destroying the micronucleus.
Without a micronucleus, meiosis cannot take place, preventing sexual exchange of genetic material during conjugation.
The micronucleus undergoes meiosis to form haploid pronuclei exchanged between conjugating cells.

Key Concept

Nuclear Dualism and Conjugation in Ciliates
Estimated Time:1m 0s
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Topics

Kingdom Protista: Protozoa and Unicellular Algae

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