HO-21 - BIO 320 lecture 21 Reading Ch 18 Ch 13 Question...

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BIO 320 lecture 21 Reading: Ch 18 (& Ch 13) Question bank D-II & text Gene regulation in eukaryotes Transcription initiation In eukaryotes, as in prokaryotes, gene expression is regulated: not all genes are expressed at once. The basic mechanism for regulating transcription is the same as in prokaryotes: regulatory proteins bind to specific DNA sequences to activate or repress transcription from promoters. However, eukaryotic regulatory regions tend to be larger and more complex . Also, the extra steps in eukaryotic gene expression - mRNA processing and transport to the cytoplasm - provide more opportunities for regulation. start site promoter elements enhancer (or upstream activation sequence) Regulating transcription initiation: enhancers complex of transcription factors and RNA polymerase II basal transcription An activator protein bound to an enhancer increases the transcription initiation rate from a basal level by interacting with TFs and RNA polymerase. DNA looping can bring distant enhancers close to the promoter; this also means that enhancers can be either upstream or downstream of the genes they regulate. enhanced transcription Coordinated gene regulation : – eukaryotic genes are not arranged in operons, but different genes with the same enhancer sequences can be regulated by the same activator proteins.
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