Micronucleus is the name given to the small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division. It usually is a sign of genotoxic events and chromosomal instability. The macronucleus controls non-reproductive cell functions , expressing the genes needed for daily functioning. The micronucleus is the generative, or germline nucleus, containing the genetic material that is passed along from one generation to the next.
Paramecium reproduces asexually, by binary fission. How do paramecia defend themselves? Generally, Paramecium species are able to defend themselves by means of mechanical extrusomes like trichocysts that will be discussed later on this chapter but Didinium seems to overcome the defense of Paramecium by means of a highly specialized combination of extrusomes.
Do ciliates have a nucleus? Unlike other eukaryotes, ciliates have two different nuclei: a large macronucleus and one or many small micronuclei. The macronucleus contains the genes that are used to regulate cell functions, and the micronuclei contain genes that are involved in sexual reproduction.
Do ciliates have flagella? The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella.
How long does a paramecium live? The tiny paramecium, however, does not. He perishes only when food runs out, when his stream dries up or when he meets acme other accident. If all goes well this tiny animal can live a hundred, a thousand or even a million years. What disease does paramecium cause? In this process, the genome of the micronucleus is amplified resulting in many copies of a single set of chromosome s.
This occurs usually during conjugation. Reference s : 1 Cavalier-Smith, T. Flagellate megaevolution: the basis for eukaryote diversification. In: Leadbeater, B. The Flagellates. Unity, diversity and evolution. London: Taylor and Francis, pp. Meet some of New Zealand's unique fauna, including endemic insects, frogs, reptiles, birds, and mammals, and investigate.. This tutorial looks at sex determination via the sex chromosomes, X and Y.
Thus, micronucleus is responsible for the genetic reorganization that occurs during conjugation or cross-fertilization. Not only that, but micronucleus also gives rises to the macronucleus.
However, the genome of micronucleus is transcriptionally silent. In addition to these, micronucleus contains a comparatively small amount of DNA. The macronucleus is the larger nucleus present in ciliate protozoa. It contains somatic genome that has heredity information of the organism.
Compared to micronucleus, macronucleus consists of a higher amount of DNA in hundreds to thousands of chromosomes. DNA in macronucleus controls the metabolism of the organism. Therefore, it is the centre of metabolic activities of the organism. In fact, macronucleus is responsible for the normal functioning of the cell.
Thus, it is the non-reproductive nucleus of ciliate protozoa. Moreover, macronucleus is ellipsoidal in shape, and it is active in transcription. Macronucleus disintegrates during conjugation. But, it reforms from the micronucleus by karyogamy. Ciliates have two nuclei as micronucleus and macronucleus.
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