genes are expressed cant mate as yeast can only mate with other mating type

Genes are expressed cant mate as yeast can only mate

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genes are expressed, can’t mate as yeast can only mate with other mating type Mutants with both mating types have faulty silencing regions i.e. faulty histones Gene repression RAP1 binds to DNA in silencer regions and in repetitive sequences in telomeres, recognized by SIRs SIR1, SIR3, and SIR4 interact with RAP1 to silence DNA SIR2 deacetylates histone tails, causing DNA to condense Deacetylated regions recruits more SIR2, positive feedback reaction Histone Code Deacetylation causes chromatin to condense, silencing DNA o Ume6 is a transcription factor that binds to specific region of DNA with its DNA binding domain
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o Ume6 repressor domain recruits Sin3 which is part of a large protein complex called a co-repressor, histone deacetylase complex o Co-repressor contains Rpd3 which deacetylates histone tails Acetylation causes chromatin to open up, allowing transcription o Gcn4 is a transcription factor that binds to specific region of DNA with its DNA binding domain o Gcn4 activation domain recruits co-activator complex, acetyl transferase, which contains Gcn5 which acetylates histone tails Methylation and phosphorylation can activate or deactivate depending on location Trimethylation of lysine 9 on histone 3 (H3K9me3) recognized by HP1 (heterochromatin protein 1), which recruits histone methyltransferase which makes more H3K9me3 marks, causes spreading of heterochromatin (dense, transcriptionally inactive chromatin) Chromatin Immunoprecipitation (ChIP) 1. Isolate and cut chromatin into small chunks 2. Mix with antibody against mark of interest, antibody bound to beads 3. Precipitate beads to retrieve chromatin with mark of interest 4. Isolate this chromatin and do next generation sequencing to see what genes undergo that modification Can do this for whole genome and then determine if a particular gene of interest was present in that precipitant Dosage Compensation Females have 2 X chromosomes, one needs to be silenced, takes place very early in embryonic development One X or the other is silenced for all cells, females are mosaic Inactive X chromosomes are Barr Bodies XIST is a non-coding RNA that coats X to inactivate it Epigenetic traits – transmitted independently of the DNA sequence itself Higher order chromatin configurations and their characteristic markers influence the way the genes are read, giving rise to epigenetic traits E.g. Xist is a noncoding RNA that causes heterochromatin spreading by modifying histones, thus silencing X Developmental restrictions – controls where genes are to be expressed in the body i.e. Antennapedia Imprints – marks on specific genes determining if they will be expressed, sex specific DNA marks – cytosine in CpG rich regions of DNA are methylated, which is recognized by mSin3, a histone deacetylase, which changes chromatin configuration
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Histone marks e.g. H3K9me3 recognized by HP1, brings in histone methyltransferase to condense chromatin
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