Chromatin - • epigenetic change change in gene expression...

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Chromatin, Posttranscription effect of chromatin structure on gene expression - DNA organized around histones into nucleosomes DNA methylation - blocks accidental transcription of genes that are turned off o vertebrates have protein that binds to methylated base pairs, prevents transcription from starting o ensures that genes stay turned off when turned off coactivators add acetyl groups to amino acids in chromatin >> makes DNA accessible to transcription factors remove high order chromatin structure >> faster transcription eukaryotic posttranscriptional control - uses regulatory proteins, small RNA small RNAs - interacts directly w/ main gene transcripts to regulate gene expression o 21-28 nucleotides long o RNA interface - inhibition of genes by RNA o double-stranded RNA forms when 2 ends complementary to each other loop o dicer - enzyme that makes small RNAs o microRNAs (miRNA) - binds directly to mRNA, prevents translation o small interfering RNAs (siRNA) - degrades mRNA before they get translated
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Unformatted text preview: • epigenetic change - change in gene expression passed down in generations o not caused by changes in DNA sequence o due to changes in DNA packaging • changing how strands twist >> changes which genes are more easily accessible for expression • primary transcript- initial mRNA molecule copied by RNA polymerase o includes introns/exons o spliceosomes (made of snRNPs) cut out the introns o alternative splicing >> creates different proteins from same gene • RNA editing- produces altered mRNA not coded for the genome, usually through deamination • nuclear membrane makes sure that only completely processed transcripts reach the cytoplasm • translation factors- controls how mRNA gets translated by ribosomes o translation repressor protein - binds to beginning of transcript >> mRNA can’t attach to ribosomes • transcripts for regulatory proteins, growth factors less stable than other mRNA, more easily degraded by other enzymes...
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