14
Enzyme contains two sites
(1) catalytic site (2) regulator/allosteric site
Exposure of bacterial cells to lactose increases levels of lactose-utilizing enzymes
1,000- to 10,000-fold
In the trpL gene, which stem-loop together with the U-rich attenuator sequence acts as an intrinsic terminator
3-4
Who discovered attentuation by studying the trp operson?
Charles Yanofsky
The rate of transcription initiation rarely influences gene expression
False; the most common way that bacteria regulate gene expression is by influencing the rate of transcription initiation
Can a particular segment of mRNA from the trpL operon participate in the formation of more than one stem-loop at the same time?
NO (if region 3 is pair with region 2, its bases are not available to pair with Region 4)
What regulation refers to control of proteins already present in the cell?
Posttranslational
In the E. coli thiMD operon, the 5' end of the mRNA folds into a structure with a stem-loop called the * that keeps the Shine-Dalgarno sequence accessible to the ribosome
Shine-DalGarno antisequestor
when TPP levels are high,
TPP binds to the RNA as it is being made and causes a change in its secondary structure
In the trp operson, trptophan acts as
a corepressor
The product of an operon may act as a * if the operon is repressible
corepressor
Sequential use of sugars by a bacterial cell is called *
diauxic growth
Product of lacA encodes
galactoside transacetylase; covalentely modifies lactose and lactose analogs by the attachment of hydrophobic acetyl groups (allows them to safely move out of the cell w/o toxic buildup)
When four molecules of allolactose are bound to lac repressor, and repressor can no longer bind to operator, and RNA pol is free to transcribe the operon, the operon has been ______
induced
Types of * include disulfide bond formation and attachment of prosthetic groups
posttranslational covalent modification
In an operon, the _______ signals the beginning of transcirption
promoter
A corepressor is a small molecular that binds to a *protein, thereby causing the protein to bind to the DNA, while an * binds to an activator protein and prevents it from binding to the DNA
repressor, activator
why does transcription of the trp operon continue when tryptophan levels are low?
ribosome pauses in region 1, prevent the 3-4 stem-loop from forming
When TPP levels are low,
secondary structure stem-loop (antiterminator) prevents the formation of the terminator stem-loop (so transcription of entire thi operon occurs)
The mRNA from the trpL genes has four regions that are complementary to each other and cause the mRNA to form *
stem loops
The mRNA made from the trpL gene contains codons for 14 amino acids that form
the trp leader peptide
Riboswitches can regulate
transcription (TPP riboswitch in e. coli) or translation (TPP riboswitch in B subtillis)
trp operon
trp C,A,B,E,D
The lac repressor does not completely inhibit transcription oft the lacZ, lacY, lacA
true
β-ONPG can b used to detect levels of β-galactosidase, bc β-gal cleaves -ONPG into a substane with a * color
yellow
An operon is a group of two or more genes under the transcriptional control
a single promoter
The transport of glucose into bacteria cell causes the intracellular level of c-AMP to fall because the enzyme __________________ is inhibited
adenylyl cyclase
The lac repressor protein binds to the operator and
blocks transcription
Effector molecules influence gene expression by binding to
inhibitor and activators
In feedback inhibition, the final product in a metabolic pathway
inhibits an enzyme that acts early in the pathway
Corepressor for a repressible operon
is the product of that operon
The intracellular concentration of the inducer ___________ remains high as long as lactose is available in the envi
allolactose
The small effector molecular produced by the enzyme adenylyl cyclase is *
cAMP
When the lac repressor binds to the lac _____ site, RNA pol cannot transcribe the lac Z-Y-A genes
operator
Anabolic enzymes are usually encoded by ______ operons, and _____ usually encode catabolic enzymes
repressible; inducible
A regulatory protein that binds to DNA and inhibits transcription is a
repressor
A regulatory site on a protein that is not the active site is called an _________-
allosteric site
The RNA transcribed from the micF gene is complementary to the ompF mRNA and acts as a(n) * strand
antisense
Why is a merozygote better at complementing a mutation in a trans-acting factor than in a cis-acting element?
bc cis-acting must be adjacent to the gene it is regulating
What effect would either a loss-of-function mutation in the lac I gene or a mutation in operator that prevents repressor binding have?
both result in constitutive expressin of the lac operon
Polycistronic mRNA
contains the sequences of two or more genes
When only * is present, allolactose and cAMP levels are high
lactose
Product of lacY gene
lactose permease; transport lactose into the bacterial cell
Why is transcriptiion of the lac operon low when both lactose and glucose are present
low levels of the cAMP result in CAP not binding to the CAP site
A translational repressor protein binds to
mRNA near the start codon
When TPP levels are low, the mRNA of the E.coli thiMD operon forms a stem-loop structure that
makes the Shine-Dalgarno sequence available to the ribosome
riboswitch
mechanism for regulating transcription, translation, RNA stability, and splicing in which an RNA molecule can switch btwn two secondary conformations based on whether or not a small molecule, such as TPP, binds to the RNA
Name of a strain of bacteria containing F' factor?
merozygote
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 2+ genes under the transcriptional control of a single promoter
operon
Allolactose is a small effector molecule that binds to the lac repressor and
prevents repressor from bidning to DNA
