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