Question

why do tetrahymena have so many nuclei and what are they for? Please explain!

Answer 1

Tetrahymena are free living ciliated protozoans found in aquatic regions. They exhibit a unique feature called Nuclear Dimorphism. Due to this feature they are used as a model organism for molecular research. It has two nuclei with different functions.

It has a germline micronucleus and a somatic macronucleus. The micro nucleus is diploid and contains five pairs of chromosomes. It is transcriptionally silent. The micro nucleus acts as the store house of genetic information for sexual prodigy.

The macronucleus is derived from the micronucleus. The micronucleus is the vegetative germ-line during which the macronucleus is transcribed, translated and transmitted to the next asexual generation by mitosis. Macronucleus is expressed only during vegetative replication. It contains approximately 300 chromosomes which are derived from micronucleus chromosomes.

The template activity of DNA in the micronucleus is highly restricted compared to that in the macronucleus. Micronuclei synthesize and contain little RNA and do not contain either nucleoli or ribonucleoprotein granules. Macronuclei synthesize and contain large amounts of RNA and have many nucleoli and ribonucleoprotein granules. Macro and micronuclei also have distinct differences in the timing of DNA synthesis during the cell cycle and in the timing and mechanism of nuclear division. During conjugation the macronucleus becomes pycnotic and disappears while the micronucleus undergoes meiosis and fertilization, ultimately giving rise to new macro and new micronuclei.