Saccharomyces_A

Located near the telomeres on each arm of chromosome

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Unformatted text preview: s switch mating type came from the discovery of two additional copies of the MAT locus called HML and HMR. Located near the telomeres on each arm of chromosome III, the HML and HMR loci are transcriptionally silent. In wild-type strains, HML contains information and HMR contains a information. The mechanism of mating type switching involves a transposition of mating type information from the transcriptionally silent HML or HMR locus into the transcriptionally active MAT locus. Switching occurs only in the a and cell types. a/ cells do not switch even if they carry HO because the a1 and 2 regulators repress transcription of the HO gene. A simple way to understand the mechanism of mating type switching in homothallic strains is to imagine an analogy with a cassette tape recorder. A cell can retrieve a cassette of mating type information located in an HML or HMR storage locus and insert it into the MAT playback locus. The cell retrieves information from the storage locus by a series of steps. The product of the HO gene, a sitespecific endonuclease, initiates the process. The HO-encoded enzyme makes a double-stranded cut in chromo...
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This note was uploaded on 10/03/2013 for the course BI 206 taught by Professor Celenza during the Spring '08 term at BU.

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