Chapter 14
Negative
--------- control is transcriptional regulation by repressor proteins.
cris, trans
A ------- -effect is mediated by a DNA element that binds regulator proteins, whereas a -------- -effect is mediated by genes that encode diffusible regulatory proteins.
cis-acting
A DNA segment that must be adjacent to the gene that it regulates is known as a(n) ----- - ------ element.
Blank 1: allolactose Blank 2: operator or lacO
A conformational change in the lac repressor protein occurs upon binding of the sugar ------ to it. This change in shape prevents the repressor from binding to the ------- site.
Blank 1: allolactose Blank 2: operator or lacO
A conformational change in the lac repressor protein occurs upon binding of the sugar ------- to it. This change in shape prevents the repressor from binding to the ------- site.
inducer
A small effector molecule that increases the rate of transcription is called a(n) ----------.
operon
A(n) ------- is a cluster of genes that are part of a single transcription unit that is under the control of a single promoter.
CAP site
An activator protein recognizes the ______ of the lac operon.
polycistronic
An mRNA that encodes more than one protein is called ------- mRNA.
inducible
An operon that can be turned on in the presence of a small effector molecule is said to be a(n) ------- operon.
Transcription Post-translation Translation
At what levels does gene regulation occur in prokaryotes?
Regulatory transcription factors
Both positive and negative control
β-galactosidase
Break down of lactose into galactose and glucose
differentiation
Cell ______ is the process by which cells become specialized into particular types.
Lac operator
Cis-acting element
Galactoside transacetylase
Covalent modification of lactose and lactose analogues
Cis-effect
Effect mediated by a cis-acting element
negative, positive
Gene expression can be regulated in two main ways. Repressor proteins are used for ----- control of gene expression, and activator proteins are used for -------- control of gene expression.
When CAP and cAMP bind to the CAP site, this enhances binding of RNA polymerase to the promoter site.
How do CAP and cAMP increase the transcription of the lac operon?
It binds to the repressor protein and prevents it from binding to the operator site of the lac operon.
How does allolactose affect the lac repressor protein?
By only expressing the gene product when it is needed in the cell.
How does gene regulation help conserve energy for an organism?
When lactose is present, the lac repressor protein does not bind to the operator site and transcription can occur. When lactose is present, transcription of the lac operon is high.
How does the presence of lactose in the cell influence the transcription of the lac operon?
only when lactose is present
In E. coli, the genes required to metabolize lactose are expressed ______.
hemoglobin
In mammals, the protein which delivers oxygen to body cells is --------.
operator
In the lac operon, the _______ is the DNA sequence at which the lac repressor binds.
Repressor
Negative control
coordinate the regulation of genes with related functions
Operons enable bacteria to ______
coordinate the regulation of genes with related functions
Operons enable bacteria to ______.
lacY
Permease
encodes more than one protein
Polycistronic mRNA ______.
Activator
Positive control
Activitor
Proteins that bind to DNA and increase the rate of transcription are called -------.
Trans-effect
Regulation by a diffusible factor
regulation of RNA processing
Regulation of prokaryotic gene expression typically involves all of the following mechanisms EXCEPT:
regulation of RNA processing
Regulation of prokaryotic gene expression typically involves all of the following mechanisms EXCEPT: - regulation of RNA processing - regulation of translation - regulation of transcription - modifications to proteins after translation
Promotor
Regulatory transcription factors influence the expression of genes by affecting the rate of transcription. They do so by binding directly to DNA at or near the ------ site.
energy
Some proteins are produced only when needed. This is an example of gene regulation that conserves -------.
inducible
The binding of an effector molecule increases the rate of transcription of the lac operon. Thus, it is said to be a(n) ------- operon.
lacl
The figure is a representation of the lac operon. Match each number to the appropriate gene. 1?
lacZ
The figure is a representation of the lac operon. Match each number to the appropriate gene. 2?
lacA
The figure is a representation of the lac operon. Match each number to the appropriate gene. 4?
lac operon in the absence of lactose
The following diagram shows which type of operon?
to repress transcription of the lac operon
The function of the protein encoded by lacI is ______.
Gene expression
The functional product of genes arises from what process?
lactose
The genes found in the lac operon of E.coli are used for the metabolism of -------.
must be adjacent to the genes that it regulates
The lac operator is an example of a cis-acting element because it ______.
CAP
The lac operon is also under positive control by an activator protein called what?
Inducible operon
The lac operon is an example of what type of operon?
Blank 1: RNA Blank 2: polymerase or pol
The lac repressor protein prevents the transcription of the lac operon genes by the enzyme ------ -------
repressor
The lacI gene encodes the lac -------.
allolactose
The molecule that serves as the inducer of the lac operon is
expression
The process in which the information in a gene is made into a functional gene product, such as an RNA molecule or a protein, is termed gene --------.
Lac repressor
Trans-acting factor
Lactose permease
Transport of lactose across the cell membrane
When the concentration of lactose is low in the cell
Under what conditions does the lac repressor bind to the operator of the lac operon and prevent transcription?
Proteins that bind to DNA and affect the transcription of one or more genes
What are regulatory transcription factors?
lacY Promoter lacZ lacA
What are the basic components of the lac operon?
The transport of lactose across the cell membrane The modification of lactose and lactose analogues The breakdown of lactose
What are the three major functions of the enzymes encoded by the lac operon?
Promoter, operator, and three structural genes
What does the lac operon region contain?
A small effector molecule that increases the rate of transcription
What is an inducer?
A cluster of genes under the transcriptional control of a single promoter
What is an operon?
The process by which cells become specialized in different types
What is cell differentiation?
A small effector molecule involved in the positive control of the lac operon
What is cyclic AMP (cAMP)?
operator
he lacO of the lac operon is the site where the repressor protein binds. It is referred to as the ------.
lacZ
β-galactosidase
i promoter
In this schematic of the lac operon, match each letter to the appropriate DNA element. A?
CAP site
In this schematic of the lac operon, match each letter to the appropriate DNA element. B?
lacP
In this schematic of the lac operon, match each letter to the appropriate DNA element. C?
lacO
In this schematic of the lac operon, match each letter to the appropriate DNA element. D?
repressor
Regulatory transcription factors that bind to DNA and decrease the rate of transcription are termed -------.
lac Y
The figure is a representation of the lac operon. Match each number to the appropriate gene. 3?
operator
The lacO of the lac operon is the site where the repressor protein binds. It is referred to as the ------.
prevent transcription of the lac operon
The protein encoded by the lacI gene functions to:
the lac operator
The transcription of the lac operon genes is inhibited when the lac repressor protein binds to ______.
lac operon in the presence of lactose
This diagram is a representation of which type of operon?
lacA
Transacetylase
positive
Transcriptional regulation by activator proteins is a type of regulation called ------ control.
positive
Transcriptional regulation by activator proteins is a type of regulation called ------- control.
The sequence of nucleotides that is recognized by an activator protein
What is the CAP site for the lac operon?
Bacteria can coordinate the expression of multiple genes in the same biological pathway.
What is the advantage of operon organization in bacteria?
The metabolism of lactose
What is the function of the genes that are expressed in the lac operon of E. coli?
Allolactose
What is the inducer molecule for the lac operon?
They bind to DNA and decrease the rate of transcription.
What is the role of repressor proteins in the regulation of transcription?
Galactoside transacetylase β-galactosidase Lactose permease
What proteins are produced by the three structural genes in the lac operon?
Lactose permease β-galactosidase Galactoside transacetylase
What proteins are produced by the three structural genes in the lac operon?
activator
When ______ proteins bind to DNA, they increase the rate of transcription.
The genes for lactose metabolism are expressed when lactose is present but not when it is absent.
When are the genes involved in lactose metabolism in E. coli expressed and when are they turned off?
transcribe
When geneticists say a gene is "turned on," they mean that it is ------ into mRNA.
When very little or no mRNA is transcribed from the gene
When is a gene "turned off"?
negative
When transcription is regulated by repressor proteins, this is called ______ control.
positive
When transcription of a gene is regulated by activator proteins, the gene is under ______ control.
lacI
Which of the following genes encodes the lac repressor protein?
When allolactose is produced, this causes the transcription of the lac operon.
Why is the lac operon considered inducible?
Hemoglobin
______ is the main protein that delivers oxygen to cells of a mammal's body.
