Question
BIOLOGY ap
Control_of_Gene_Expression
Control of Gene Expression in Prokaryotes
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.
1.What type of operon is illustrated? An inducible operon
2.Consider the operon. Other than the gene that regulates the
operon, how many genes are contained within the operon? Three
3.Where on the DNA strand does RNA polymerase bind to start
transcription, the promoter, the operator or the terminator? The RN
polymerase binds to the promoter
4.Which direction is the RNA polymerase moving? From the 3’
end to the 5’ end (Left to Right)
5.In which diagram is transcription and translation occurring
successfully, diagram A or diagram B? Justifyyour answer with
evidence. Transcription is occurring in diagram B because it shows
mRNA and proteins being made from DNA.
6.Consider the non-science meaning of the following terms.
Match the purpose with each of these sections in the operon in
terms of gene transcription.
?Promoter
oSpot
where transcription begins
?Operator
oSpot
where transcription begins
?Terminator
oOn/Off
switch
7.Refer to diagram A.
a.What protein does the regulatory gene produce? A repressor
protein
b.To what section of the operon does this protein bind? The
repressor protein binds to the operator site.
c.Propose an explanation for why transcription is not
occurring in diagram A. The repressor protein is blocking the RNA
polymerase, therefore transcription cannot occur.
8.Refer to Diagram B.
a.When an inducer molecule attaches to the repressor protein,
what happens to the repressor protein? The repressor protein
changes shape
b.How does the change identified in part a allow
transcription of the genes in the operon to occur? The repressor
protein is no longer binding to the operator. Because of this,
transcription
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