overview of transcriptional control - important for adaptation, development, homeostasis
- regulating promoter access - controls start of transcription
- binding proteins to regulatory sequence blocks/catalyzes binding of RNA polymerase
- promoter (nucleotide sequence) tells polymerase where to start transcribing
- transcriptional control in prokaryotes - prokaryotes grow/divide as quickly as possible
- adjusts cell’s activities to immediate environment
- reversible changes, lets cell adjust enzymes levels up/down
- transcriptional control in eukaryotes - eukaryotes protected from changes in immediate environment
- regulates body as a whole, not just individual cells
- controls growth/development
- enzymes for a particular developmental change stops working after the change takes place
- posttranscriptional control - changes mRNA produced by transcription
DNA-binding motifs - proteins have special structure to bind to DNA on major groove
- major groove - contains hydrogen atoms, hydrogen bond donors/acceptors, hydrophobic methyl groups
- helix-turn-helix - most common motif
- made up of 2 alpha-helical segments connected by nonhelical segment
- recognition helix - fits into major groove of DNA molecule
- more protein-DNA-binding sites increases strength of bond between them
- homeodomain motif - helix-turn-helix motfi in center
- zinc finger motif - uses zinc to coordinate binding to DNA
- more zinc fingers in cluster >> stronger link between protein/DNA
- leucine zipper motif - 2 different protein subunits make a single binding site
- Y-shape, allows for greater flexibility in gene control
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