BIO 140 CH. 14 Connect CONCEPTS

In the trpL gene, which stem-loop together with the U-rich attenuator sequence acts as an intrinsic terminator

3-4

An operon is a group of two or more genes under the transcriptional control of

A single promoter

What happens when levels of allolactose rise inside an E. Coli cell?

Allolactose binds to the lac repressor and prevents it from binding to the operator.

T/F: Gene expression is always the same

False

T/F: The rate of transcription initiation rarely influences overall gene expression

False

The trp operon is regulated by a repressor protein and by ______ in which transcription is stopped prematurely

attenuation

Transcription begins but terminates before the entire mRNA is made during ________

attenuation

The conversion of a riboswitch form one conformation to another is due to

binding of a small molecule

During attenuation, transcription begins

but it is terminated before the entire mRNA is made

When the lac repressor is bound to the operator, RNA polymerase _______ the lacZ, lacY, or lacA genes

cannot transcribe

Inducible operons usually encode ______ enzymes, and repressible operons usually encode _________ enzymes

catabolic; anabolic

The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is ___________ __________.

catabolite repression

Posttranslational regulation refers to ____________-

control of proteins already in the cell

In catabolite repression, transcription is influenced by the presence of _______

glucose

In feedback inhibition, the final product in a metabolic pathway ________

inhibits an enzyme that acts early in the pathway

An operon encodes a _____ mRNA, an RNA that contains the sequences of two or more genes

polycistronic

The term ________ regulation refers to control of proteins already present in the cell.

posttranslational

In the thi operon, when the levels of TPP are low, the mRNA folds into a stem-loop structure that

prevents formation of the terminator stem-loop

Phenomenon in which the level of gene expression can vary under different conditions is gene

regulation

When lactose is depleted from the environment, the

Intracellular concentration of allolactose fails

A polycistronic mRNA contains the sequence(s)

of 2+ genes

In the trpl sequence, the 3-4 stem-loop together with the U-rich attenuator sequence acts as a(n) ___________ ____________

intrinsic sequence

In the trpL gene, the 3-4 stem-loop together with the U-rich attenuator sequence acts as an _________________ ________________

intrinsic terminator

When the tryptophan level in the cell is _______, the ribosome pauses in region one of the trpL mRNA, causing region 2 to bind to region 3 and transcription to continue.

low

A translational repressor recognizes sequences within _______ and _____ translation

mRNA; inhibits

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

An _______ is a group of two or more genes under the transcriptional control of a single promoter

operon

The research of Jacob and Monod provided

our initial understanding of gene regulation

An RNA molecule that can exist in two different secondary conformations and thereby affect gene regulation is known as a(n) ___________

riboswitch

In bacteria, the most common way to regulate gene expression is by influencing

the rate of transcription regulation

Riboswitches can regulate

transcription or translation

The TPP riboswitch in E.coli controls _______, whereas the TPP riboswitch in B. sutilis controls ______

translation; transcription

Why does transcription of the trp operon continue when tryptophan levels are low?

The ribosome pauses in region 1, preventing the 3-4 stem-loop from forming

The intracellular concentration of the inducer ____ remains high as long as lactose is available in environment

allolactose

In the thi operon, when levels of TPP are low, the 5' end of the mRNA forms an __________ stem-loop structure that allows transcription to continue

antiterminator

Anabolic enzymes are usually encoded by ______ operons, and _________ operons usually encode catabolic enzymes

repressible; inducible

Studies indicate that the lac operon has ____ operator site(s) for the lac repressor

three

The research of Monod and Jacob that led to the initial understanding of gene regulation stemmed from an interest in

enzyme adaptation

The genes in the trp operon encode

enzymes used in tryptophan biosynthesis

As levels of allolactose increase within an E. coli cell, allolactose binds to the lac _________, promoting a conformational change that prevents binds to the _______site on the DNA

repressor, operator

When the product of a gene produced in a metabolic pathway inhibits an enzyme that acts early on in the pathway it is called __________ ____________

feedback inhibition

In attenuation, transcription

is stopped prematurely

A regulatory protein that inhibits translation is called a __________ ________

translational repressors

Select the genes in the trp operon

trpE, trpD, trpC, trpB, and trpA,