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Published byThomasine Garrett Modified over 9 years ago
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Gene Regulation in Prokaryotes - plasmid, not protected by nuclear envelope - DNA is not bound up with histones -One of the best known pathways is the lac Operon
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Lac Operon contains 1. a promoter (the specific nucleotide sequence tells a cell to begin transcription, RNA Polymerase binds here) 2. an operator (segment of DNA used to turn gene expression on or off, repressor protein binds here) 3. Three genes
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Operation of the Lac Operon Lac Operon is turned OFF by the Repressor Protein – Binds with operator (segment of DNA) to prevent a gene from being transcribed. Lac Operon is turned ON by the presence of Lactose – Binds to repressor protein to prevent it from adhering to DNA so RNA Polymerase binds and begins transcription
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Without Lactose:
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With Lactose:
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Eukaryotic Gene Regulation: Only a few of the available genes will be expressed in the cells of different tissues Complex!
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Eukaryotic Gene Regulation: TATA box - repeating TATATATA’s signal that the gene is ahead!
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Proteins that bind to enhancer sequences of a gene can work to: a.Open up tightly packed chromatin. b.Attract RNA polymerase. c. Block access to genes.
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Fig. 14.9, p. 229 unit of transcription in a DNA strand exonintron mature mRNA transcript poly-A tail 5’ 3’ (snipped out) exon intron cap transcription into pre-mRNA 3’5’ RNA Editing
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Hox genes
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Development and Differentiation Hox genes are master control genes that control the differentiation of cells and tissues in the embryo. A mutation in hox gene in fruit flies had a leg growing where antenna should be.
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