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12-5 Gene Regulation Eukaryotic Gene Regulation How are most eukaryotic genes controlled? Slide 1 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Eukaryotic Gene Regulation Many eukaryotic genes have a sequence called the TATA box; it is part of the promoter. Upstream enhancer TATA box Promoter sequences Introns Exons Direction of transcription Slide 2 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Eukaryotic Gene Regulation The TATA box seems to help position RNA polymerase, so that transcription can occur. Upstream enhancer TATA box Promoter sequences Introns Exons Direction of transcription Slide 3 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Eukaryotic Gene Regulation Eukaryotic promoters are usually found just before the TATA box, and consist of short DNA sequences. Upstream enhancer TATA box Promoter sequences Introns Exons Direction of transcription Slide 4 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Development and Differentiation Development and Differentiation As cells grow and divide, they undergo differentiation, meaning they become specialized in structure and function. Hox genes control the differentiation of cells and tissues in the embryo. They are master genes—lay out the body plan; tell other genes to do their thing Slide 5 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Slide 6 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Slide 7 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Slide 8 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Slide 9 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Slide 10 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Development and Differentiation Hox Genes are universal to animals Fruit fly chromosome Mouse chromosomes Fruit fly embryo Mouse embryo Adult fruit fly Copyright Pearson Prentice Hall Adult mouse Slide 11 of 26 12-5 Gene Regulation Gene Regulation: An Example How are genes turned on and off in PROKARYOTIC CELLS, like bacteria??? Slide 12 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Gene Regulation: An Example Bacteria turn on/off genes, too. An example of this are the “lac” genes The lac genes (genes to use lactose) are turned off by repressors and turned on by the presence of lactose. You only want to make the digestive proteins when needed…. Thus, being able to turn on/off genes is an example Slide of FEEDBACK. Think of a thermostat…. 13 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Gene Regulation: An Example On one side of the operon's three genes are two regulatory regions. • In the promoter (P) region, RNA polymerase binds and then begins transcription. Slide 14 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Gene Regulation: An Example • The other region is the operator (O). Slide 15 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Gene Regulation: An Example When the lac repressor binds to the O region, transcription is not possible. Slide 16 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Gene Regulation: An Example When lactose is added, sugar binds to the repressor proteins. Slide 17 of 26 Copyright Pearson Prentice Hall 12-5 Gene Regulation Gene Regulation: An Example The repressor protein changes shape and falls off the operator and transcription is made possible. Slide 18 of 26 Copyright Pearson Prentice Hall
