Chapter 16
Unregulated genes are also called
Constitutive genes
What type of regulator does not need to be adjacent to the gene(s) it is regulating?
Trans-acting factor
When lactose is depleted from the environment, the _______.
the intracellular concentration of allolactose falls
The product of the lacY gene is required for ______.
the transport of lactose into the bacterial cell
Why is a merozygote better at complementing a mutation in a trans-acting factor than in a cis-acting element?
A cis-acting element must be adjacent to the gene it is regulating.
The operon is flanked by a sequence called a(n)_ that signals the beginning of transcription and one termed a(n) _ that signals the end of transcription.
Blank 1: promoter Blank 2: terminator
What effect would a loss-of-function mutation in the lacI gene and a mutation in operator that prevents repressor binding have?
Both result in constitutive expression of the lac operon.
Monod, Jacob, and Pardee learned about the lac operon using bacterial strains called merozygotes. Since lacI encodes a diffusible protein, in a merozygote, the gene on the _ could supply the mutant cell with functional repressor protein.
F factor
True or false: Effector molecules influence gene expression by binding to DNA.
False
True or false: Gene expression is always the same.
False
True or false: On a regulatory protein, an allosteric site is the same as the active site.
False
True or false: The rate of transcription initiation rarely influences overall gene expression.
False
In the 1950s, which three scientists studied mutations in the lac operon of E. coli?
Monod Jacob Pardee
How does an effector molecule influence gene expression?
The effector molecule binds to a regulatory protein and affects its ability to bind DNA.
True or false: The lac repressor does not completely inhibit transcription of the lacZ, lacY, and lacA genes.
True
Enzyme adaptation refers to the observation that ______.
a particular enzyme appears within a cell only after the cell has been exposed to the substrate for that enzyme
An operon is a group of two or more genes under the transcriptional control of ______.
a single promoter
Would rescue of a mutation using a merozygote better indicate regulation of a gene by a trans-acting factor or a cis-acting element?
a trans-acting factor
A regulatory protein that binds to DNA and increases the rate of transcription is a(n) ______.
activator
When the lac repressor is bound to the operator, RNA polymerase ______ the lacZ, lacY, or lacA genes.
cannot transcribe
The lacY gene encodes lactose_, a membrane protein
permease
Enzyme adaptation results from the synthesis of specific ______ in response to lactose in the environment.
proteins
Constitutive genes encode proteins that the cell needs ______.
all the time
What is the name for a strain of bacteria containing an F' factor?
merozygote
A protein such as a repressor that inhibits transcription is exerting ____ _ control of transcription.
negative
It has been shown that the lac operon has three_ sites to which the lac repressor can bind.
operator
When the lac repressor binds to the lac_ site, RNA polymerase cannot transcribe the lacZ, lacY or lacA genes.
operator
A loss-of-function mutation in a gene encoding a repressor protein has the same effect as a mutation in the ______.
operator site
A group of two or more genes under the transcriptional control of a single promoter is called a(n)
operon
Transcription regulation by an activator protein is considered to be ______ control.
positive
Experiments by Jacob and Monod demonstrated that enzyme adaptation is due to the regulation of genes during
transcription
A polycistronic mRNA contains the sequence(s) for ______.
two or more genes
The three protein-encoding genes in the lac operon are
lacZ,lacY,lacA
Monod and Jacob studied _ metabolism in E. coli.
lactose
Genes that are regulated by corepressors or inhibitors are called
repressible genes
A regulatory protein that binds to DNA and inhibits transcription is called a(n)
repressor
A conformational change that prevents the repressor from binding to the lac operator occurs when _ binds to the lac repressor.
allolactose or lactose
A regulatory site on a protein where an effector molecule binds is called a(n) _ site.
allosteric
In the absence of lactose, the lac repressor ______.
allows very small amounts of lac operon enzymes to be made
The lac repressor protein binds to the operator and ______.
blocks transcription
The small effector molecule produced by the enzyme adenylyl cyclase is ______.
cAMP
Many bacterial species use sugars sequentially. This is called ______.
diauxic growth
The sequential use of sugars by a bacterial cell is called
diauxic growth
The normal lacI gene on the F' factor could rescue the lacI- mutants because the product of the lacI gene encodes a ______.
diffusible protein
The phenomenon in which the level of gene expression can vary under different conditions is
gene regulation
In catabolite repression, transcription is influenced by the presence of ______.
glucose
The transport of ______ into a cell causes a(n) _______ in the concentration of cyclic-AMP by inhibiting adenylate cyclase.
glucose; decrease
Monod, Jacob, and Pardee identified rare E. coli mutants that ______.
had abnormal lactose adaptations
An inducer is a small effector molecule that causes the rate of transcription to ______.
increase
Genes that are regulated by inducers are called _ genes.
inducible
The ______ gene encodes a repressor protein.
lacI
Allolactose is a small effector molecule that binds to the lac repressor and ______.
prevents the repressor from binding to DNA
The binding of ______ to the lac repressor promotes a conformational change that prevents the repressor from binding to the lac operator.
allolactose
The intracellular concentration of the inducer _ remains high as long as lactose is available in the environment.
allolactose
The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is
catabolite repression
A DNA segment that must be adjacent to the gene(s) it regulates is a
cis acting element
Which are functions of the enzyme β-galactosidase?
cleaves lactose into glucose and galactose converts lactose into allolactose
The probability that allolactose will bind to the lac repressor depends on the allolactose_ in the bacterial cell.
concentration, amount, or level
In an operon, the ______ signals the beginning of transcription.
promoter
In bacteria, the most common way to regulate gene expression is by influencing the ______.
rate of transcription initiation
An inducer could bind to a(n) ______ and prevent it from binding to the DNA, or it could bind to a(n) ______ and cause it to bind to the DNA.
repressor, activator
The CAP site and the operator site are ______ that function in gene regulation.
short DNA segments