Editing Tetrahymena (section)

== ''T. thermophila'':  a model organism in experimental biology ==
[[Image:Tetrachimena Beta Tubulin.png|thumb|200px|[[Tubulin|β-tubulin]] in ''Tetrahymena''.]]

As a ciliated [[protozoan]], ''Tetrahymena thermophila'' exhibits [[nuclear dimorphism]]: two types of cell [[Cell nucleus|nuclei]].  They have a bigger, [[Somatic cell|non-germline]] [[macronucleus]] and a small, [[germline]] [[micronucleus]] in each cell at the same time and these two carry out different functions with distinct cytological and biological properties. This unique versatility allows scientists to use ''Tetrahymena'' to identify several key factors regarding [[gene expression]] and genome integrity.  In addition, ''Tetrahymena'' possess hundreds of [[cilia]] and has complicated [[microtubule]] structures, making it an optimal model to illustrate the diversity and functions of microtubule arrays.

Because ''Tetrahymena'' can be grown in a large quantity in the laboratory with ease,  it has been a great source for biochemical analysis for years, specifically for [[Enzyme|enzymatic]] activities and purification of [[Cell (biology)#Subcellular components|sub-cellular components]].  In addition, with the advancement of genetic techniques it has become an excellent model to study the gene function ''in vivo''. The recent sequencing of the macronucleus genome should ensure that ''Tetrahymena'' will be continuously used as a model system.

''Tetrahymena thermophila'' exists in seven different sexes ([[mating type]]s) that can reproduce in 21 different combinations, and a single tetrahymena cannot reproduce sexually with itself.  Each organism "decides" which sex it will become during mating, through a [[stochastic]] process.<ref name="PLOS2013">{{cite journal | vauthors = Cervantes MD, Hamilton EP, Xiong J, Lawson MJ, Yuan D, Hadjithomas M, Miao W, Orias E | display-authors = 6 | title = Selecting one of several mating types through gene segment joining and deletion in Tetrahymena thermophila | journal = PLOS Biology | volume = 11 | issue = 3 | pages = e1001518 | year = 2013 | pmid = 23555191 | pmc = 3608545 | doi = 10.1371/journal.pbio.1001518 | doi-access = free }}</ref><ref>{{cite journal |last1=Quirk |first1=Trevor |title=How a microbe chooses among seven sexes |journal=Nature |date=27 March 2013 |pages=nature.2013.12684 |doi=10.1038/nature.2013.12684 |s2cid=179307103 }}</ref>

Studies on ''Tetrahymena'' have contributed to several scientific milestones including:
# First cell which showed synchronized division, which led to the first insights into the existence of mechanisms which control the [[cell cycle]].<ref name="whitepaper">{{cite web | first = Eduardo | last = Orias | name-list-style = vanc | date = 10 February 2002 | url = http://www.lifesci.ucsb.edu/~genome/Tetrahymena/SeqInitiative/WhitePaper.htm | title = Sequencing the Tetrahymena thermophila Genome White Paper | work = National Human Genome Research Institute }}</ref>
# Identification and purification of the first [[cytoskeleton]] based [[motor protein]] such as ''[[dynein]]''.<ref name="whitepaper" />
# Aid in the discovery of ''[[lysosomes]]'' and ''[[peroxisomes]]''.<ref name="whitepaper" />
# Early molecular identification of somatic genome rearrangement.<ref name="whitepaper" />
# Discovery of the molecular structure of ''[[telomeres]]'', ''[[telomerase]]'' enzyme, the templating role of telomerase RNA and their roles in cellular senescence and chromosome healing (for which a Nobel Prize was won).<ref name="whitepaper" />
# Nobel Prize–winning co-discovery (1989, in Chemistry) of catalytic [[RNA]] (''[[ribozymes|ribozyme]]'').<ref name="whitepaper" /><ref>{{cite journal | vauthors = Kruger K, Grabowski PJ, Zaug AJ, Sands J, Gottschling DE, Cech TR | title = Self-splicing RNA: autoexcision and autocyclization of the ribosomal RNA intervening sequence of Tetrahymena | journal = Cell | volume = 31 | issue = 1 | pages = 147–57 | date = November 1982 | pmid = 6297745 | doi = 10.1016/0092-8674(82)90414-7 | s2cid = 14787080 }}</ref>
# Discovery of the function of [[histone]] [[acetylation]].<ref name="whitepaper" />
# Demonstration of the roles of [[posttranslational modification]] such as acetylation and glycylation on [[tubulins]] and discovery of the enzymes responsible for some of these modifications (glutamylation)
# Crystal structure of 40S ribosome in complex with its initiation factor eIF1
# First demonstration that two of the "universal" [[stop codon]]s, UAA and UAG, code for the amino acid [[glutamine]] in some eukaryotes, leaving UGA as the only termination codon in these organisms.<ref>{{cite journal | vauthors = Horowitz S, Gorovsky MA | title = An unusual genetic code in nuclear genes of Tetrahymena | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 82 | issue = 8 | pages = 2452–5 | date = April 1985 | pmid = 3921962 | pmc = 397576 | doi = 10.1073/pnas.82.8.2452 | bibcode = 1985PNAS...82.2452H | doi-access = free }}</ref>

[[File:Tetrahymena-research.png|350px|left|thumb|Main fields of biomedical research where ''Tetrahymena'' cells are used as models]]
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