Final answer:
The micronucleus in ciliates like Paramecium is vital for sexual reproduction, where it undergoes meiosis and mitosis to facilitate genetic exchange and diversity. It remains inactive in gene transcription, contrary to the macronucleus which manages cellular functions and requires reconstruction due to genetic imbalance over time.
Step-by-step explanation:
Description of Micronucleus
The micronucleus is a critical cellular structure found in ciliate protists such as Paramecium. It is characterized as a smaller, diploid nucleus that is essential for sexual reproduction. Unlike the macronucleus, the micronucleus does not participate in the transcription of genes for cellular processes; instead, it remains somewhat inactive until conjugation occurs. During sexual reproduction, organisms such as Paramecium begin by making physical contact and forming a cytoplasmic bridge. The micronuclei of each cell then undergo meiosis, followed by mitosis, leading to an exchange of haploid nuclei between the cells. This fusion results in a genetically novel diploid micronucleus. As the conjugation process progresses, the micronucleus undergoes additional rounds of mitosis, and the macronucleus is eventually reconstructed from a subset of the micronuclear DNA, which gets edited and undergoes DNA replication to form smaller chromosomes specific for cellular functions.
These processes ensure genetic diversity and the healthy continuation of the species. The macronucleus, on the other hand, is responsible for the daily metabolic activities of the cell and undergoes amitotic division, leading to eventual genetic imbalance and necessitating periodic reconstruction from the micronucleus during sexual reproduction.