Regulating Genes Only a fraction of genes in

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Regulating Genes

Regulating Genes

Only a fraction of genes in a cell are expressed (made into RNA) at

Only a fraction of genes in a cell are expressed (made into RNA) at any given time. How does the cell decide which will be turned on and which will stay “silent”? PROMOTER regions You already know about _______ that show RNA polymerase where to start. REGULATORY SITES that There are other ___________ control whether a gene is ON or OFF.

Typical Gene Structure Section 12 -5 Regulatory sites Promoter (RNA polymerase binding site) Start

Typical Gene Structure Section 12 -5 Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand Stop transcription

E. Coli lac operon Group of genes that operate together are OPERON called an

E. Coli lac operon Group of genes that operate together are OPERON called an ________ Genes code for enzymes needed to digest lactose sugar. Only needed if glucose is not available

Most of time glucose is available so OFF by a lac operon is turned

Most of time glucose is available so OFF by a lac operon is turned _____ REPRESSOR ______ molecule that sits on a regulatory site next to the promoter OPERATOR called the ______

What if there’s NO GLUCOSE? Cells need to get rid of the repressor ON

What if there’s NO GLUCOSE? Cells need to get rid of the repressor ON and turn _____the lac genes to digest lactose instead. The presence of lactose causes a change in the ______ REPRESSOR molecule so so it can’t bind the operator site.

Cells turn genes ON & OFF as needed Many genes are regulated by REPRESSOR

Cells turn genes ON & OFF as needed Many genes are regulated by REPRESSOR _______ proteins that keep them turned off until needed. Others use proteins that speed up transcription ________ or affect protein synthesis __________

EUKARYOTES are more COMPLEX Additional regulatory sequences: ENHANCER regions 1. ______ upstream from promoters

EUKARYOTES are more COMPLEX Additional regulatory sequences: ENHANCER regions 1. ______ upstream from promoters bind many different regulatory proteins TATA box 2. _____ (TATATA or TATAAA) helps position RNA POLYMERASE Image by Riedell

http: //highered. mheducation. com/sites/dl/fre e/0072835125/126997/animation 27. html

http: //highered. mheducation. com/sites/dl/fre e/0072835125/126997/animation 27. html