When Paramecium undergoes sexual reproduction, what is exchanged between conjugant partners?
The correct answer and explanation is:
In sexual reproduction of Paramecium, the conjugant partners exchange micronuclei.
During conjugation, two Paramecium cells come together and align side by side, forming a bridge between them. The process begins with the exchange of genetic material, specifically the micronucleus. Each Paramecium has two types of nuclei: a large macronucleus and a small micronucleus. The macronucleus controls the cell’s metabolic activities, while the micronucleus plays a role in sexual reproduction.
The first step in conjugation involves the pairing of two Paramecium cells. The micronucleus of each cell undergoes meiosis, producing four haploid micronuclei. Three of these are disintegrated, and the remaining haploid micronucleus from each cell is exchanged between the conjugants. The exchange of micronuclei ensures genetic recombination.
Once the exchange has occurred, the micronuclei fuse with the micronucleus of the other Paramecium, forming a diploid zygotic nucleus. This new zygotic nucleus then undergoes mitotic division, giving rise to new micronuclei. Some of these newly formed micronuclei undergo differentiation to become macronuclei, which control the metabolic functions of the cell.
Conjugation allows for genetic diversity in Paramecium populations, as the fusion of two genetically distinct cells leads to offspring that carry a mix of traits from both parents. This process is different from asexual reproduction, where the organism simply divides into two genetically identical offspring. Sexual reproduction helps to ensure survival in changing environments by promoting genetic variability, which can increase the adaptability of the population.