Gene Regulation Section 12–5 This section explains how some genes in prokaryotes and eukaryotes are controlled

Gene RegulationGene Regulation Section 12–5Section 12–5

This section explains how some genes This section explains how some genes in prokaryotes and eukaryotes arein prokaryotes and eukaryotes are

controlled.controlled.

Gene StructureGene Structure

Gene Regulation:Gene Regulation:

Where does RNA polymerase bind?Where does RNA polymerase bind?

It binds to the promoter.It binds to the promoter.


Is the following sentence true or false? Is the following sentence true or false?

The actions of DNA-binding proteins help The actions of DNA-binding proteins help to determine whether a gene is turned on to determine whether a gene is turned on or turned off.or turned off.


What is an operon? What is an operon?

It is a group of genes that is operated It is a group of genes that is operated together.together.


What is the function of the genes in the What is the function of the genes in the lac lac operon? operon?

They must be expressed for They must be expressed for E. coli E. coli to use to use lactose as a food.lactose as a food.


Circle the letter of each sentence that is true about Circle the letter of each sentence that is true about lactose.lactose.

To use lactose for food, To use lactose for food, E. coli E. coli must take must take lactose across its cell membrane.lactose across its cell membrane.

The bond between glucose and galactose must The bond between glucose and galactose must be broken in order for be broken in order for E. coli E. coli to useto uselactose for food.lactose for food.


Circle the letter of the number of genes in Circle the letter of the number of genes in the the lac lac operon found in operon found in E. coli.E. coli.

• 11

• 22

• 33

• 44


What turns the What turns the lac lac operon off and on?operon off and on?

The The lac lac genes are turned off by repressors genes are turned off by repressors and turned on by the presence of lactose.and turned on by the presence of lactose.


How does the repressor protein prevent How does the repressor protein prevent transcription? transcription?

It prevents RNA polymerase from binding It prevents RNA polymerase from binding to the operator.to the operator.


How does lactose cause the How does lactose cause the lac lac operon to operon to turn on? turn on? Lactose molecules bind to the repressor Lactose molecules bind to the repressor protein, causing it to change shape so that protein, causing it to change shape so that the repressor releases the operator. the repressor releases the operator. This allows RNA polymerase to bind to the This allows RNA polymerase to bind to the promoter and transcribe the genes of the promoter and transcribe the genes of the operon.operon.


Circle the letter of each sentence that is Circle the letter of each sentence that is true about gene regulation in prokaryotic true about gene regulation in prokaryotic genes.genes.

b. b. Many other genes are regulated by Many other genes are regulated by repressor proteins.repressor proteins.c. c. Some genes are regulated by proteins Some genes are regulated by proteins that enhance the rate of transcription.that enhance the rate of transcription.

Eukaryotic Gene Regulation Eukaryotic Gene Regulation

Is the following sentence true or false? Is the following sentence true or false?

Operons are frequently found in Operons are frequently found in eukaryotes.eukaryotes.

FalseFalse

Eukaryotic Gene Regulation:Eukaryotic Gene Regulation:

How are eukaryotic genes usually How are eukaryotic genes usually controlled? controlled?

Most are controlled individually and have Most are controlled individually and have regulatory sequences that are much more regulatory sequences that are much more complex than those of the complex than those of the lac lac operon.operon.


What is the function of the TATA box?What is the function of the TATA box?

It seems to help position RNA polymerase It seems to help position RNA polymerase by marking a point just before the point by marking a point just before the point where transcription begins.where transcription begins.


Eukaryotic promoters are usually found Eukaryotic promoters are usually found just ____the TATA box, and they consist just ____the TATA box, and they consist of a series of short ____sequences.of a series of short ____sequences.

beforebefore

DNADNA


List three ways in which proteins that bind to List three ways in which proteins that bind to enhancer sequences of a gene can work to enhancer sequences of a gene can work to regulate gene expression.regulate gene expression.

a.a. They open up tightly packed chromatin.They open up tightly packed chromatin.

b.b. . . They help to attract RNA polymerase.They help to attract RNA polymerase.

c.c. They block access to genes.They block access to genes.


Why is gene regulation in eukaryotes more Why is gene regulation in eukaryotes more complex than in prokaryotes? complex than in prokaryotes?

All of the cells in a multicellular organism carry All of the cells in a multicellular organism carry the complete genetic code in their nucleus, but the complete genetic code in their nucleus, but only a few of the available genes can be only a few of the available genes can be expressed in the appropriate cells of different expressed in the appropriate cells of different tissues. tissues.

Complex regulation allows for this specificity.Complex regulation allows for this specificity.

Development and Differentiation Development and Differentiation

What role do the hox genes play in the What role do the hox genes play in the development of an organism? development of an organism?

They control the differentiation of cells and They control the differentiation of cells and tissues in the embryo.tissues in the embryo.

Development and DifferentiationDevelopment and Differentiation

Circle the letter of each sentence that is true about Circle the letter of each sentence that is true about hox genes.hox genes.

In fruit flies, a mutation affecting the hox genes In fruit flies, a mutation affecting the hox genes can replace a fly’s antennae with acan replace a fly’s antennae with apair of legs.pair of legs.

The function of the hox genes in humans seems The function of the hox genes in humans seems to be almost the same as it is in fruitto be almost the same as it is in fruitflies.flies.

Development and DifferentiationDevelopment and Differentiation

Why do common patterns of genetic Why do common patterns of genetic control for development exist among control for development exist among animals?animals?

All the genes that control development All the genes that control development have descended from the genes of have descended from the genes of common ancestors.common ancestors.

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Gene Regulation Section 12–5 This section explains how some genes in prokaryotes and eukaryotes are controlled