Regulation of Gene Expression
TRUE
(T/F) As long as the repressor is bound to the operator, no mRNA (and, therefore, no proteins) are made
TRUE
(T/F) If the repressor is BOUND to the operator, the polymerase is blocked and does not produce mRNA
TRUE
(T/F) In bacteria, the structural genes that encode proteins involved in a particular metabolic pathway are often found sequentially grouped on the chromosome along with the cis-acting elements that regulate the transcription of these genes
TRUE
(T/F) In yeast, a unicellular organism, the genes required to metabolize galactose are on different chromosomes
TRUE
(T/F) The lacl gene has its own promoter and is not part of the lac operon.
TRUE
(T/F) When glucose and lactose are available: RNA pol is unable to effec- tively initiate transcription, even though the repressor is not bound to the 0 site
TRUE
(T/F) Transcriptional attenuation does not occur in eukaryotes because the presence of a membrane-bound nucleus spatially and temporally separates transcription and translation.
active
(active/inactive) In the absence of glucose, adenylyl cyclase is_______, and cAMP is made and binds totheCAP.
negative
(positive/negative) trp operon is subjed to______ control.
inhibition
(stimulation/inhibition) Elevated levels of ppGpp result in_______ of rRNA synthesis
transcription activation domain (TAD)
A domain of the specific transcription factor (STF) that recruits coactivators, such as histone acstyltransfsrasss and the general transcription factors that, along with RNA pol, are required for formation of the transcription initiation complex at the promoter.
lacl gene
A regulatory gene, the_______, codes for the repressor protein (a trans-acting factor) that binds to the O site with high affinity.
Glucose
Adenylyl cyclase is inactive in the presence of_____
transcription
As with the prokaryotes,_______ is the primary site of regulation
glucose
Bacteria use_______, if available, as a fuel in preference to any other sugar.
attenuation
Because repression by Trp is not always complete, the trp operon, unlike the lac operon, is also regulated by a process known as______.
formation of a truncated, nonfunctional peptide product
Because transcription and translation are temporally linked in prokaryotes (seep. 454), attenuation also results in the ________that is rapidly degraded
zinc fingers
Binding of Gal4 to UASGal through______ in itS DBD occurs in both the absence and presence of galactose
Gal3
Binds Gal80, thereby allowing Gal4 to activate transcription
Allolactose
Binds to a repressor protein, causing a conformational change that prevents the repressor binding to the operator
Gal4 (Gal =galactose)
Coordinated expression is mediated by the protein______, a STF that binds to a short regulatory DNA sequence upstream of each of the genes.
Hormone response elements (HRE)
DNA sequences that bind trans-acting proteins and regulate gene expression in response to hormonal signals in multicellular organisms.
Amino acid biosynthesis
During elevated levels of ppGp, synthesis of mRNa for enzymes required for _______ is not inhibited
galactose circuit
Examples of coordinate regulation in eukaryotes include the _______
zinc finger leucine zipper helix-turn-helix
Examples of structural motifs
r-protein Shine- Dalgarno (SD) sequence
For each operon, one specific______ functions in the repression of 1ranslation of the polycistronic mRNA from that operon. The r-protein does so by binding to the_______ located on the mRNA jus1 upstream of 1he first initia1ing AUG codon (see p. 448) and acting as a physical impediment 10 the binding of the small ribosomal subunit 10 the SD sequence.
Transcription of DNA to RNA
For most genes, the main site of control is the ______
lacY gene
Gene that codes for permease, which facilitates the movement of lactose into the cell
constitutive encode products
Genes required for basic cellular functions and so are expressed at essentially a constant level
Gal4 protein
Glucose prevents the use of glactose by inhibiting expression of ____
reversibly binding a protein known as the repressor
How does the operator regulates the activity pf the structural genes?
7
How many operons does ecoli have?
r-protein
If 1he concentration of rRNA falls, the_____ then is available to bind its own mRNA and inhibit its translation.
operon
If Trp becomes scarce, the______ is expressed.
RNA polymerase (RNA pol)
If the operator is NOT BOUND by the repressor,_______ binds the promoter, passes OVER the operator, and reaches the protein-coding genes that it transcribes to mRNA
hairpin (stem-loop) strudure
IfTrp is plentiful, transcription initiation that escaped repression by Trp is attenuated (stopped) by the formation of an attenuator, a ______in the mRNA similar to that seen in rho- independent termination (
lacl general
In contrast to the inducible lacZ, lacY, and lacA genes, whose expression is regulated, the______ is constitutive
specific transcription factor (STF)
In coordinated regulation, it functions as a specific transcription factor (STF) that binds to a cis-acting regulatory consensus sequence on each of the genes in the group even if they are on different chromosomes
transcription
In prokaryotes such as the bacterium Escherichia coli (E. coli), regu- lation of gene expression occurs primarily at the level of________
binding of trans-acting proteins to cis-acting regulatory elements on their single DNA molecule (chromosome)
In prokaryotes such as the bacterium Escherichia coli (E. coli), regulation of gene expression is mediated by _____
eukaryotes
In_________, gene expression also involves extensive posttranscriptional and posttranslational processe
Ribosomes
Initiates translation of mRNA as it is being transcribed
excess of 1heir own protein products
Operons for ribosomal pro- teins (r-proteins) can be inhibited by ______
eukaryotes
Operons, however, are not found in______, which mus1 use alternate strategies to solve 1he problem of how to coordina1ely regulate all the genes required for a specific response
stringent response
Regulation in response to amino acid starvation is known as the ______
regulatory sequences of DNA
Regulation of transcription is controlled by __________that are usually embedded in the noncoding regions of the genome.
Hairpin structure
Self-complementary sequences in certain regions of the mRNA cause a ______ to form, which attenuates (prematurely terminates) transcription
Trp
The 5'-end of the mRNA contains two adjacent codons for_____
cAMP regulatory protein (CRP)
The CAP is sometimes called____
cAMP-CAP trans-acting complex
The ______ binds to the CAP site, causing RNA pol to initiate transcription with high efficiency at the promoter site
alarmone guanosine tetraphosphate (ppGpp).
The binding of an uncharged transfer RNA (tRNA) to the A site of a ribosome triggers a series of events that leads to the production of the ______.
structural motifs
The binding of proteins to DNA is made through ______
lacl gene
The gene product pd this lac gene, the repressor protein, is always made and is active unless the inducer is present.
cis-acting
The regulatory DNA sequences are called________ because they influence expression of genes on the SAME chromosome as the regulatory sequence
trans-acting
The regulatory molecules are called__________ because they can diffuse (transit) through the cell from their site of synthesis to their DNA-binding sites (
operator (0) and the catabolite activator protein (CAP) sites
The regulatory portion of the operon consists of _______where regulatory pro- teins bind
promoter region
The regulatory portion of the operon consists of the _______where RNA pol binds
upstream
The regulatory portion of the operon is______ of the three structural genes.
upstream activating sequence Gal (UASGal)
The sequence is called the________.
stringent factor (RelA)
The synthesis of this unusual derivative of guanosine diphosphate (GDP) is catalyzed by_______, an enzyme physically associated with ribosomes
lac operon
The_______ contains the genes that code for three proteins involved in the catabolism of the disaccharide lactose
Cis-acting elements
These are DNA sequences that are bound by transacting regulatory factors
allolactose
This compound is an inducer that binds to the repressor protein, changing its conformation so that it can no longer bind to the 0 site.
tryptophan (trp) operon
This operon contains five structural genes that code for enzymes required for the synthesis of the amino acid tryptophan
Galactose circuit
This regulatory scheme allows for the use of galactose when glucose is not available
one r-protein
Thus,______ inhibits synthesis o f all 1he r-proteins of the operon.
polycistronic messenger RNA
Transcription product that results from bacterial operons
prokaryotes
Transcriptional attenuation can occur in______ because translation of an mRNA begins before its synthesis is com- plete.
when the O site is empty and the CAP site is bound by a complex of cyclic adenosine monophosphate ([cAMP]
When are the lacZ. lacY, and lacA genes maximally expressed?
catabo- lite repression
When both glucose and lactose are available: Adenylyl cyclase is inhibited in the presence of glucose (a process known as _____)so no cAMP-CAP complex forms, and the CAP site remains empty.
uninduced negligible
When both glucose and lactose are avallable: the lac operon is______, and transcription is_______, even if lactose is present at a high concentration
helix-tum-helix motif
When only glucose Is avallable and the lac operon is repressed (turned off), repression is mediated by the repressor protein binding via a_______ to the O site, which is downstream of the promoter
induced, maximally expressed or turned on
When only lactose is available, the lac operon is _____
Gal3
When present, galactose activates ____ protein
Gal80
When the sugar is absent, the regulatory protein ______ binds Gal4 at its TAD, thereby inhibiting gene transcription.
energy is not wasted making unneeded gene products
Why is it that regulating the first step in the expression of a gene in prokayrotes an efficient approach?
attenuation
With this process, transcription is initiated but is terminated well before completion
chromosome 6 chromosome 11
a protein transcription factor, which is a trans-acting molecule regulates a gene on _________might itself have been produced from a gene on________
transcript
a single polycistronic mRNA molecule that contains three sets of start and stop codons
thiogalactoside transacetylase
acetylates lactose
Lactose Glucose
all of the lac gene are maximally produced only when ____ is available to the cell and _____ is not
constitutive encode products
also known as "housekeeping" genes
allolactose
an isomer of lactose
ppGpp
binds RNA poland alters promoter selection through use of different sigma factors for the pclymerase
r- protein
binds to rRNA and with a higher affinity than for mRNA
Induction
causes a 50-fold enhancement over basal expression.]
permease
facilitates the movement of lactose into the cell
use of deoxyribonucleic acid (DNA) for the synthesis of RNA (transcription)
first step in gene expression
LacZ gene
gene that codes for Beta-galactosidase,
Lac A
gene that codes for thiogalactoside transacetylase, which acetylates lactose
Regulation of transcription
initial step in all gene expression
alternative mRNA splicing and polyadenylation, control of mRNA stability, and control of 1ranslational efficiency
major modes of posttranscrip1ional regulation at the mRNA level are________
Gene expression
multistep process that uhimately results in the production of a functional gene product, either ribonucleic acid (RNA) or protein.
inducible lactose (lac) operon
operpn of Ecoli
synthesis of RNA (transcription)
primary site of regulation in both prokaryotes and eukaryote
operator
segment of DNA that regulates the activity of the structural genes of the operon
Trans-acting factors
synthesized from genes that are DIFFERENT from the genes targeted for regulation
operon
the structural genes that encode proteins involved in a particular metabolic pathway are often found sequentially grouped on the chromosome along with the cis-acting element and the entire package is known as ____
lac Z Lac Y Lac A
what are the genes that code for three proteins involved in the catabolism of the disaccharide lactose
inducer molecule
when an_______ is present, it binds to the repressor, causing the repressor to change shape so that it no longer binds the operator.
