Chapter 14

True or false: Gene regulation is constant.

False

How does an effector molecule influence gene expression? -The effector molecule binds to the mRNA and affects the ability of the ribosome to initiate translation. -The effector molecule binds to a regulatory protein and affects its ability to bind DNA. -The effector molecule causes the mRNA to form a stem/loop structure that blocks the ribosome. -The effector molecule binds to DNA and affects the ability of RNA polymerase to initiate transcription.

-The effector molecule binds to a regulatory protein and affects its ability to bind DNA.

In bacteria, the most common way to regulate gene expression is by influencing ______. -the rate of transcription initiation -the rate of transcription elongation -the rate of translation initiation -the frequency of cell division

-the rate of transcription initiation

True or false: Effector molecules influence gene expression by binding to DNA.

False Reason: An effector molecule exerts its effects by binding to a repressor or activator.

An operon is a group of two or more genes under the transcriptional control of ______. -different polymerases -a single promoter -two or more promoters

-a single promoter

In an operon, the ______ signals the beginning of transcription. -ribosome binding site -terminator -origin -promoter

-promoter

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

polycistronic

A regulatory protein that binds to DNA and inhibits transcription is a(n) ____.

repressor

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

attenuation

The phenomenon in which the level of gene expression can vary under different conditions is ____.

gene regulation

When the lac repressor binds to the lac ____ site, RNA polymerase cannot transcribe the lacZ, lacY or lacA genes.

operator, nucleotides, or O

A(n) ____ is a group of two or more genes under the transcriptional control of a single promoter.

operon

Constitutive genes ______. -are regulated by glucose levels. -respond to amino acid levels in the cell. -respond to lactose levels in the cell. -are unregulated.

-are unregulated.

When the lac repressor is bound to the operator, RNA polymerase ______ the lacZ, lacY, or lacA genes. -cannot transcribe -transcribes one of -increases transcription of

-cannot transcribe

Inducible operons usually encode ______ enzymes, and repressible operons usually encode ______ enzymes. -catabolic; anabolic -anabolic; catabolic

-catabolic; anabolic

Anabolic enzymes are usually encoded by ______ operons, and ______ operons usually encode catabolic enzymes. -inducible; repressible -repressible; inducible

-repressible; inducible

In attenuation, transcription ______. -continues to the transcription stop site -never starts -proceeds half-way through the operon -is stopped prematurely

-is stopped prematurely

A polycistronic mRNA contains the sequence(s) ______. -for genes from different operons -of two or more genes -for several genes and control regions -for only one gene

-of two or more genes

he operon is flanked by a ____ that signals the beginning of transcription and a ____ that signals the end of transcription.

Blank 1: promoter Blank 2: terminator

True or false: The rate of transcription initiation rarely influences overall gene expression.

False

True or false: Gene expression is always the same.

False Reason: Gene expression can vary under different conditions.

Unregulated genes are also called ____.

Constitutive genes

Unregulated genes have ______ -variable levels of expression. -constant or variable levels of expression depending on the gene. -constant levels of expression.

-constant levels of expression.

A regulatory protein that increases the rate of transcription is a(n) ____.

activator