Histone Acetylation – allow the histone to pack less tightly, allowing transcription to proceed. Methylation of cytosine – inactivates DNA transcriotion. Deacetylation and Methylation are two repressors in gene expression. Noncoding RNAs Play Multiple Roles in Controlling Gene Expression • A small percentage of the genome codes for proteins, rRNA and tRNA (& other small RNAs)- Assumed that the rest of the DNA was untranscribed & didn’t have anything important• Effects on mRNAs by MicroRNAs and Small Interfering RNAs- MicroRNAs = miRNAs *Single stranded RNA molecules *Capable of binding to complementary sequences in mRNA molecules *Formed from precursor RNA, which folds back on itself (held together by H-bonds)
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