Control of Gene Expression in Prokaryotes
How do prokaryotes use operons to control gene expression?
Why?
Houses usually have a light source in every room, but it would be a waste of energy to leave every light on
all the time, so there are switches to turn off the lights in rooms that are not in use. Sometimes one switch
controls several lights in the same room. Likewise, prokaryotic cells can turn genes on and off based on
environmental factors. Sometimes related genes are grouped together with one switch. This group of
genes, along with the sections of DNA that regulate them, is called an operon.
Model 1 – An Inducible Operon
Diagram A Regulatory Promoter Operator Terminator
Gene
DNA Gene X Gene Y Gene Z
RNA polymerase
5´
mRNA 3´
Repressor
protein
Diagram B Regulatory Promoter Operator Terminator
Gene
DNA Gene X Gene Y Gene Z
RNA
polymerase
3´
5´
mRNA
Active Inducer Inactive
repressor molecule repressor Protein X Protein Y Protein Z
protein protein
Control of Gene Expression in Prokaryotes
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1
https://www.coursehero.com/file/47549659/17-Control-of-Gene-Expression-in-Prokaryotes-S-2019pdf/
, 1. What type of operon is illustrated in Model 1?
inducible
2. Consider the operon in Model 1. Other than the gene that regulates the operon, how many
genes are contained within the operon?
3
3. In Model 1, where on the DNA strand does RNA polymerase bind to start transcription, the
promoter, the operator or the terminator?
The promoter
4. Which direction is the RNA polymerase moving in Model 1?
5 to 3
5. In which diagram of Model 1 is transcription and translation occurring successfully, diagram A
or diagram B? Justify your answer with evidence from Model 1.
Diagram B because the repressor is inactivesotranscription task
6. Consider the nonscience meaning of the following terms. Match the purpose with each of these
sections in the operon in terms of gene transcription.
Promoter Spot where transcription ends
Operator Spot where transcription begins
Terminator On/Off switch
7. Refer to diagram A in Model 1.
a. What protein does the regulatory gene in Model 1 produce?
Repressor
b. To what section of the operon does this protein bind?
The promoter
c. Propose an explanation for why transcription is not occurring in diagram A.
The repressor is active
2 POGIL™ Activities for AP* Biology
This study source was downloaded by 100000836551366 from CourseHero.com on 02-21-2022 03:44:38 GMT -06:00
https://www.coursehero.com/file/47549659/17-Control-of-Gene-Expression-in-Prokaryotes-S-2019pdf/
How do prokaryotes use operons to control gene expression?
Why?
Houses usually have a light source in every room, but it would be a waste of energy to leave every light on
all the time, so there are switches to turn off the lights in rooms that are not in use. Sometimes one switch
controls several lights in the same room. Likewise, prokaryotic cells can turn genes on and off based on
environmental factors. Sometimes related genes are grouped together with one switch. This group of
genes, along with the sections of DNA that regulate them, is called an operon.
Model 1 – An Inducible Operon
Diagram A Regulatory Promoter Operator Terminator
Gene
DNA Gene X Gene Y Gene Z
RNA polymerase
5´
mRNA 3´
Repressor
protein
Diagram B Regulatory Promoter Operator Terminator
Gene
DNA Gene X Gene Y Gene Z
RNA
polymerase
3´
5´
mRNA
Active Inducer Inactive
repressor molecule repressor Protein X Protein Y Protein Z
protein protein
Control of Gene Expression in Prokaryotes
This study source was downloaded by 100000836551366 from CourseHero.com on 02-21-2022 03:44:38 GMT -06:00
1
https://www.coursehero.com/file/47549659/17-Control-of-Gene-Expression-in-Prokaryotes-S-2019pdf/
, 1. What type of operon is illustrated in Model 1?
inducible
2. Consider the operon in Model 1. Other than the gene that regulates the operon, how many
genes are contained within the operon?
3
3. In Model 1, where on the DNA strand does RNA polymerase bind to start transcription, the
promoter, the operator or the terminator?
The promoter
4. Which direction is the RNA polymerase moving in Model 1?
5 to 3
5. In which diagram of Model 1 is transcription and translation occurring successfully, diagram A
or diagram B? Justify your answer with evidence from Model 1.
Diagram B because the repressor is inactivesotranscription task
6. Consider the nonscience meaning of the following terms. Match the purpose with each of these
sections in the operon in terms of gene transcription.
Promoter Spot where transcription ends
Operator Spot where transcription begins
Terminator On/Off switch
7. Refer to diagram A in Model 1.
a. What protein does the regulatory gene in Model 1 produce?
Repressor
b. To what section of the operon does this protein bind?
The promoter
c. Propose an explanation for why transcription is not occurring in diagram A.
The repressor is active
2 POGIL™ Activities for AP* Biology
This study source was downloaded by 100000836551366 from CourseHero.com on 02-21-2022 03:44:38 GMT -06:00
https://www.coursehero.com/file/47549659/17-Control-of-Gene-Expression-in-Prokaryotes-S-2019pdf/
