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