Chapter 12: Gene Regulation
At what levels does gene regulation occur in prokaryotes?
Post-translation Transcription Translation
What are regulatory transcription factors?
Proteins that bind to DNA and affect the transcription of one or more genes
The lacI gene is
constitutively expressed at low levels
In humans, a cell can become a muscle cell, kidney cell, skin cell, neuron, etc. This is an example of the process of cell _________________
differentiation
Polycistronic mRNA
encodes more than one protein
The production of the functional product of a gene is called
gene expression
A(n) ________________ is a cluster of genes that are part of a single transcription unit that is under the control of a single promoter.
operon
An mRNA that encodes more than one protein is called ________________ mRNA.
polycistronic
When transcription of a gene is regulated by activator proteins, the gene is under ________ control.
positive
________________ control is transcriptional regulation by activator proteins.
positive
Regulatory transcription factors influence the expression of genes by binding directly to DNA at or near the _______________ site and affect the rate of transcription.
promoter
Regulatory transcription factors influence the expression of genes by binding directly to DNA at or near the ________________ site and affect the rate of transcription.
promoter
Living organisms benefit from gene regulation because it conserves energy; _____________________ that are encoded by genes will be produced only when they are ___________________.
proteins; needed/required
Hemoglobin is composed of _______________ globin protein subunits, __________________ encoded by one gene and __________________ encoded by another gene.
4;2;2
What is an operon?
A cluster of genes under the transcriptional control of a single promoter
What is the advantage of operon organization in bacteria?
Bacteria can coordinate the expression of multiple genes in the same biological pathway.
An activator protein recognizes the ____________ of the lac operon.
CAP site
What is an example of cell differentiation in humans?
Cells develop the structure and function specific to nerve cells.
Which of the followings statements about genomes and proteomes is true?
Cells of an individual have the same genome, but different proteomes
Which of the following is an example of developmental gene regulation in mammals?
Different globin genes are expressed in the embryo, fetus, and adult.
Francois Jacob and Jacques Monod studied enzyme adaptation in
E. coli
What is the process by which a cell controls the level of expression of a specific gene or set of genes in a biological pathway?
Gene regulation
How can gene regulation be specific?
Specific genes are expressed at different developmental stages. Specific genes differ in expression levels from cell to cell. Specific genes are expressed only in certain cells.
What are two major benefits of gene regulation?
The conservation of energy Expression of genes at appropriate times
How do the mammalian embryo and fetus acquire oxygen from the mother's bloodstream?
The embryo and fetus remove oxygen from the mother's blood stream due to the high binding affinity of hemoglobin made during development.
When are the genes involved in lactose metabolism in E. coli expressed and when are they turned off?
The genes for lactose metabolism are expressed when lactose is present but not when it is absent.
What is the function of the genes that are expressed in the lac operon of E. coli?
The metabolism of lactose
What are the three major functions of the enzymes encoded by the lac operon?
The modification of lactose and lactose analogues The transport of lactose across the cell membrane The breakdown of lactose
What is cell differentiation?
The process by which cells become specialized in different types
What is the CAP site for the lac operon?
The sequence of nucleotides that is recognized by an activator protein
Control of gene expression takes place at what levels in eukaryotes? Select all that apply.
Translation Transcription Post-translation Processing of mRNA
When ________ proteins bind to DNA, they increase the rate of transcription.
activator
What are the basic components of the lac operon?
lacA lacZ promoter lacY
All of the following are considered part of the lac operon except
lacI
Which of the following genes encodes the lac repressor protein?
lacI
The lacI gene encodes the lac
repressor
How is β-galactosidase utilized by E. coli to metabolize lactose?
β-galactosidase is an enzyme that catalyzes the breakdown of lactose.
How does the presence of lactose in the cell influence the transcription of the lac operon?
When lactose is present, transcription of the lac operon is high. When lactose is present, the lac repressor protein does not bind to the operator site and transcription can occur.
Under what conditions does the lac repressor bind to the operator of the lac operon and prevent transcription?
When the concentration of lactose is low in the cell
The ______________ is the collection of all proteins that are expressed in a cell.
proteome
What term describes the complete set of proteins in a particular cell type?
proteome
Gene ___________________ is the ability of cells to control the expression of genes.
regulation
Regulation of prokaryotic gene expression typically involves all of the following mechanisms except
regulation of RNA processing
________________ are regulatory transcription factors that bind to DNA and decrease the rate of transcription.
repressors
The transcription of the lac operon genes is inhibited when the lac repressor protein binds to
the lac operator
True or false: The lacI gene is a part of the lac operon.
False -- The lacI gene encodes the lac repressor, which regulates the genes of the lac operon. The lacI gene itself is not considered part of the operon.
What statement correctly describes the structure of the protein hemoglobin?
Hemoglobin has four protein subunits, that are encoded by two different globin genes
How does allolactose affect the lac repressor protein?
It binds to the repressor protein and prevents it from binding to the operator site of the lac operon.
What statement about the lacI gene is true?
It is expressed in the presence or absence of lactose
What scientists studied the phenomenon of enzyme adaptation in bacteria?
Jacob and Monod
What are the three proteins that are produced by each of the structural genes in the lac operon?
Lactose permease Galactoside transacetylase β-galactosidase
What are small effector molecules?
Molecules that bind to transcription factors and change their conformation
How can gene regulation conserve energy?
Proteins that metabolize molecules such as small sugars are produced only when those sugars are available in the environment.
The lac repressor protein prevents the enzyme ______________ ______________ from transcribing the genes in the lac operon.
RNA polymerase
Which mechanisms of gene regulation are used by both prokaryotes and eukaryotes?
Regulation of transcription Post-translational regulation Regulation of translation
Which mechanisms of gene regulation are used by both prokaryotes and eukaryotes?
Regulation of translation Post-translational regulation Regulation of transcription
What is the role of repressor proteins in the regulation of transcription?
Repressor proteins bind to DNA and decrease the rate of transcription.
Hemoglobin
______ is the main protein that delivers oxygen to cells of a mammal's body.
________________ are proteins that bind to DNA and increase the rate of transcription.
activators
β-Galactosidase cleaves lactose into galactose and glucose. As a side reaction, it can also convert lactose into
allolactose
Gene regulation can be specific to types of __________________ and stages of ________________ .
cells; development
Genes that have relatively constant levels of expression in all conditions over time are said to be _________________ genes.
constitutive
When a gene is expressed constantly over time in a cell, it is a(n):
constitutive gene
Operons enable bacteria to
coordinate the regulation of genes with related functions
During mammalian development
different globin genes are expressed at different developmental stages
Cell ______ is the process by which cells become specialized into particular types.
differentiation
Repressors and activators that respond to small effector molecules have two functional regions called ________________ one is a site where the protein binds to the ________________, whereas the other is the binding site for the small effector molecule.
domains; DNA
Rank the different types of mammalian hemoglobins in terms of oxygen affinity, starting with the one that has the highest.
embryonic hemoglobin; fetal hemoglobin; adult hemoglobin
In humans, the __________ stage lasts from fertilization to 8 weeks. This is followed by the __________________ stage, which lasts until birth
embryonic; fetal
When an enzyme appears in a living cell only after the cell has been exposed to an environment in which the substrate for the enzyme is found, this is called
enzyme adaptation
____________ ____________ occurs when a particular enzyme appears within a living cell only after the cell has been exposed to the substrate for that enzyme.
enzyme adaptation
The morphologies of different cell types, such as skin cells and nerve cells, is strikingly different. This is due to the fact that the cells:
express different genes
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:
expression
Repressors are regulatory transcription _____________ that bind to the DNA and decrease the rate of transcription. This is a form of regulation called _____________ control. On the other hand, _____________ bind to the DNA and increase the rate of transcription, a form of regulation termed _____________ control.
factors; negative; activators; positive
The hemoglobin produced during the embryonic and ___________________ stages has a higher binding affinity for oxygen than does the hemoglobin produced after ________________. Therefore, the embryo and _______________________ can remove oxygen from the mother's bloodstream and use that oxygen for their own needs.
fetal; birth; fetus
In the bacterium E. coli, the enzyme β- __________________ catalyzes the breakdown of lactose.
galactosidase
Different cell types, such as skin cells and nerve cells, have different morphologies because ____________ are expressed and regulated in different ways in different cells.
genes
Different cell types, such as skin cells and nerve cells, have different morphologies because _______________ are expressed and regulated in different ways in different cells.
genes
Most ______________ in all species are regulated so the proteins they specify are produced at appropriate times and in specific amounts.
genes
Most ____________________ in all species are regulated so the proteins they specify are produced at appropriate times and in specific amounts.
genes
A cell's total DNA complement is called its
genome
The _________________ of a cell is the complete set of genes present.
genome
The different cell types of an individual contain the same ____________________, meaning they carry the same set of genes. However, their ________________________, which is the collection of proteins they make, is quite different.
genome; proteome
The domains of a transcriptional regulatory factor are parts of the protein that:
have different functions
In mammals, the protein ______________ delivers oxygen to body cells.
hemoglobin
Which of the following represents the correct order of DNA segments in the lac operon?
lacP - lacO - lacZ - lacY - lacA
The genes found in the lac operon of E.coli are used for the metabolism of:
lactose
In order to utilize lactose, an E. coli cell requires a transporter called:
lactose permease
Eukaryotes, but not prokaryotes, can regulate gene expression at the level of:
mRNA processing
________________ control is a form of transcription regulation in which a repressor protein decreases the rate of transcription.
negative
When transcription is regulated by repressor proteins, this is called
negative control
Repressor proteins are used for _______________ control of gene expression, and activator proteins are used for _______________ control of gene expression.
negative; positive
In E. coli, the genes required to metabolize lactose are expressed:
only when lactose is present
In the lac operon, the _______ is the DNA sequence at which the lac repressor binds.
operator
In the lac operon, the ______________ is the DNA sequence at which the lac repressor binds.
operator
The lacO site of the lac operon is called the ______________ and is the site where the repressor protein binds.
operator
In both prokaryotes and eukaryotes, most gene regulation occurs when cells regulate the level of _________________ of a gene.
transcription
Most gene regulation in both prokaryotes and eukaryotes occurs at the level of:
transcription
Small effector molecules bind to regulatory ________________ factors and cause conformational changes that influence their ability to bind to DNA.
transcription
In E. coli, the protein lactose permease is used to
transport lactose into the cell for metabolism