View source for Mating-type locus

{{Short description|Specialized region in genomes of some yeast}}
The '''mating-type locus''' is a specialized region in the [[genome]]s of some [[yeast]] and other [[fungi]], usually organized into [[heterochromatin]] and possessing unique [[histone methylation]] patterns. The [[gene]]s in this region regulate the [[mating type]] of the organism and therefore determine key events in its [[biological life cycle|life cycle]], such as whether it will reproduce [[sexual reproduction|sexually]] or [[asexual reproduction|asexually]]. In [[fission yeast]] such as ''[[Schizosaccharomyces pombe|S. pombe]]'', the formation and maintenance of the heterochromatin organization is regulated by [[RNA-induced transcriptional silencing]], a form of [[RNA interference]] responsible for genomic maintenance in many organisms.<ref name="Noma">Noma K, Sugiyama T, Cam H, Verdel A, Zofall M, Jia S, Moazed D, Grewal S (2004). "RITS acts in cis to promote RNA interference-mediated transcriptional and post-transcriptional silencing". Nat Genet 36 (11): 1174-80. {{doi|10.1038/ng1452}} {{PMID|15475954}}</ref> Mating type regions have also been well studied in [[budding yeast]] ''[[S. cerevisiae]]'' and in the fungus ''[[Neurospora crassa]]''.<ref name="Staben">Staben C, Yanofsky C. (1990). Neurospora crassa a mating-type region. ''Proc Natl Acad Sci USA'' 87(13):4917-21. {{PMID|2142304}} </ref>

==Mating-type switching==

In the budding yeast ''[[Saccharomyces cerevisiae]]'', mating-type is determined by two non-homologous alleles at the mating-type locus.  ''S. cerevisiae'' has the capability of undergoing mating-type switching, that is conversion of some [[ploidy|haploid]] cells in a colony from one mating-type to the other.  Mating-type switching can occur as frequently as once every generation. Switching involves [[homologous recombination]]al repair of a site specific, programmed double-strand break, a highly organized process.<ref name="Haber">{{cite journal |last1=Haber |first1=JE |title=Mating-type genes and MAT switching in Saccharomyces cerevisiae. |journal=Genetics |date=May 2012 |volume=191 |issue=1 |pages=33–64 |doi=10.1534/genetics.111.134577 |pmid=22555442|pmc=3338269 }}</ref> This process replaces one mating type allelic DNA sequence with the sequence encoding the alternative mating-type allele.  When two haploid cells of opposite mating type come into contact they can mate to form a diploid cell, a [[zygote]], that may then undergo [[meiosis]].  Meiosis tends to occur under nutritionally limiting conditions associated with [[DNA damage (naturally occurring)|DNA damage]].


== See also ==
* [[Mating of yeast]]

== References ==
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[[Category:Molecular genetics]]
[[Category:Mycology]]
[[Category:Sexual dimorphism]]
[[Category:Mating]]


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