The homothallic phenotype arises from a dominant

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Unformatted text preview: ains, switching occurs at a much higher frequency than one would expect if the switch were due to a point mutation. The homothallic phenotype arises from a dominant, functional HO allele at the HO locus on chromosome IV; by comparison, heterothallism results from a recessive loss-of-function allele (ho) at this same locus. (a) 1n (Haploid) 2n (Diploid) MATa / MATα Meiosis Mating 1n (Haploid) Mating MATa MATa 1n (Haploid) MATα Storage locus HMLα CEN MATα α2 MATa Ya Telomere α-specific genes No transcription HMLα Yα a-specific genes Figure A.11 (b) In an a cell Transcription Mcm1 ActIvator Ya Yα Transposition Transcription Mcm1 Repressors MATa Telomere Mcm1 ActIvators MATα Cassette playback Storage locus locus HMRa MATa Yα α1 MATα Switching homothallic conversion of mating type (b) (a) In an α cell MATα MATa a-specific genes Figure A.10 Mcm1 protein is both a positive and a negative regulator. (a) In an cell, Mcm 1 acts together with 1 to activate transcription of -specific genes but acts with 2...
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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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