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Ciliates reproduce asexually, by various kinds of fission. [17] During fission, the micronucleus undergoes mitosis and the macronucleus elongates and undergoes amitosis (except among the Karyorelictean ciliates, whose macronuclei do not divide). The cell then divides in two, and each new cell obtains a copy of the micronucleus and the macronucleus.
The term micronucleus may also refer to the smaller nucleus in ciliate protozoans, such as the Paramecium. In mitosis it divides by fission , and in conjugation a pair of gamete micronuclei undergo reciprocal fusion to form a zygote nucleus, which gives rise to the macronuclei and micronuclei of the individuals of the next cycle of fission.
Ciliates contain two nucleus types: a macronucleus that is primarily used to control metabolism, and a micronucleus which performs reproductive functions and generates the macronucleus. The compositions of the nuclear pore complexes help determine the properties of the macronucleus and micronucleus. [ 1 ]
The macronucleus divides via amitosis, whereas the micronucleus undergoes typical mitosis. During sexual development a new macronucleus is formed from the meiosis of the micronucleus, where the removal of transposons occurs. [1] On the division or reproduction of ciliates, the two nuclei are under several epigenetic controls.
Ciliates have two nuclei: micronucleus (germ-line cell nucleus) that does not express genes and macronucleus, where most genes are expressed, and is subject to chromatin elimination. During this process chromosomes are fragmented, chromatin eliminated and new DNA molecules with added telomeres are created.
The organism is surrounded by cilia. Balantidium coli has two developmental stages, a trophozoite stage and a cyst stage. In trophozoites, the two nuclei are visible. The macronucleus is long and sausage-shaped, and the spherical micronucleus is nested next to it, often hidden by the macronucleus.
There is a lot of evidence against ciliates being the metazoan ancestor. Ciliates have two types of nuclei: a micronucleus which is used as germline nucleus and a macronucleus which regulates the vegetative growth. [20] This division of nuclei is a unique feature of the ciliates and is not found in any other members of the animal kingdom. [21]
Like all ciliates, O. trifallax has two different types of nuclei: macronuclei, which are the site of transcription and gene expression, and micronuclei, which are only active during sexual reproduction but are otherwise transcriptionally inactive. Macronuclei are formed by the differentiation of micronuclei, which usually involves some degree ...