Chapter 7 Operons: Fine Control of Prokaryotic Transcription CopyrightThe McGraw-Hill Companies,Inc.Permission required for reproduction or display Mitchell Lewis/S
Chapter 7 Operons: Fine Control of Prokaryotic Transcription
The control of gene expression E.coli genome:over 3000 genes. -Some genes are active all the time (constant demand) -Some genes are turned off most of the time (rarely needed). Why doesn't the cell just leave all its genes on all the time?Because gene expression is an expensive process. Thus,the control of gene expression is essential to life
✓ E. coli genome:over 3000 genes. －Some genes are active all the time (constant demand). －Some genes are turned off most of the time (rarely needed). ✓ Why doesn't the cell just leave all its genes on all the time? Because gene expression is an expensive process. ✓ Thus, the control of gene expression is essential to life. The control of gene expression
Today 1.operon (concept and control Model) 2.Review basics of negative control of lac operon 3.Early mutant studies about lac operon (Discovery of the Operon) Merodiploids and what they tell us 4.Mechanism of repression (two models)
Today 1. operon (concept and control Model) 2. Review basics of negative control of lac operon 3. Early mutant studies about lac operon (Discovery of the Operon) Merodiploids and what they tell us 4. Mechanism of repression (two models)
1.operon grouping functionally related genes together so they can be regulated together easily.Such a group of contiguous(邻近的)、coordinately (并列)controlled genes is called an operon. Operon structure The control Model of Operon
1. operon grouping functionally related genes together so they can be regulated together easily. Such a group of contiguous (邻近的) 、 coordinately (并列) controlled genes is called an operon. Operon structure The control Model of Operon
7.1 The lac Operon Three genes that code for the enzymes that allow E.coli cells to use the sugar lactose E.coli Lactose used Glucose used Lag glucose ■lactose turning on the lac operon accumulating the enzymes Diauxic growth curve 二次[两期]生长曲线 2 4 6 8 10 Time (h)
7.1 The lac Operon Three genes that code for the enzymes that allow E. coli cells to use the sugar lactose glucose lactose E. coli Diauxic growth curve 二次[两期]生长曲线 turning on the lac operon accumulating the enzymes Lag