Chapter 18 Flashcards by Unknown Unknown

Bacteria can adjust their behavior according to their population density by using a communication system called [][]

quorum sensing

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During gene expression, the information in DNA is [] into RNA, and then the mRNA message is [] into a polypeptide.

transcribed; translated

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Transcription is the work of ______.

RNA polymerase

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The ribosome-binding site is a special initiation site located ______.

upstream (near the 5’ end) of the open reading frame

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The inhibition of RNA polymerase activity is termed [] regulation, whereas the enhancement of RNA polymerase activity is known as [] regulation

negative; positive

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catabolic pathways

metabolic pathways by which complex molecules are broken down.

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anabolic pathways

biochemical pathways for the synthesis of complex molecules from simpler ones.

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The synthesis of RNAs and proteins according to the instructions encoded in DNA is a process called ______.

gene expression

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induction

the process by which a signal causes expression of a gene or set of genes.
Ex: The addition of lactose to a bacterial medium causes a 1000-fold increase in the synthesis of the two proteins Lac permease and β-galactosidase.

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Shine-Dalgarno or ribosomal binding

Site ribosomes attach to the mRNA to initiate translation

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An inducer is a small effector molecule that causes transcription to ______.

increase

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The inducer of the genes for lactose utilization is a molecule called []

allolactose

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Breakdown of sugars occurs via ______ pathways, whereas the synthesis of amino acids occurs via ______ pathways.

catabolic; anabolic

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

a single promoter

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regulatory DNA elements of the lac operon

Operator

Promoter

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The process by which a specific molecule stimulates synthesis of a given protein is called []

induction

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The small effector molecule [] prevents the Lac repressor from binding to the operator site.

allolactose or inducer

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In the absence of lactose, the Lac [] binds to the operator, and this binding blocks transcription of the lac operon.

repressor

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operon

a unit of DNA composed of two or more genes transcribed as a polycistronic mRNA under the control of a single promoter and operator.

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In the lac operon, the two main regulatory DNA elements are the [] and the []

promoter; operator

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Allolactose is a small effector molecule that binds to the Lac repressor and ______.

prevents it from binding to DNA

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The Lac repressor protein binds to the operator and ______.

blocks transcription

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The lacA gene encodes a transacetylase, enzyme that covalently modifies _____.

lactose; adds acetyl groups to lactose and other sugars

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The lac operon contains three genes; lacZ, which encodes [] lacY, which encodes Lac [] and lacA, which encodes an enzyme called []

beta galactosidase; permease; transacetylase

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A constitutive mutant of the lac operon will _____.

synthesize Lac permease even in the absence of lactose

Allolactose is a small effector molecule that binds to the Lac repressor and ______.

prevents it from binding to DNA

Constitutive mutants ______.

strains in which certain gene products are made all the time, irrespective of environmental conditions.

The Lac repressor protein binds to the operator and ______.

blocks transcription

The product of which gene is not required for the breakdown of lactose?

lacA

An effector is a small molecule that _____.

binds to a protein and changes its conformation

What is the function of the operator site in the lac operon?

It serves as a binding site for the repressor.

A mutation that changes the nucleotide sequence of the []so that the repressor is no longer able to bind to the site, will cause a constitutive synthesis of the lactose-utilizing proteins.

operator

The binding of the [] to the repressor causes an allosteric effects that abolishes the repressor's ability to bind to the operator.

effector

A loss-of-function mutation in the lacI gene can have the same effect as a mutation in the _______.

operator site

A mutation in the operator that renders it nonfunctional will cause the ______.

constitutive expression of the lac operon

An element that acts in trans is typically a ______.

protein that can diffuse through the cytoplasm and act on any DNA target in the cell

What effect would either a loss-of-function mutation in the lacI gene or a mutation in t

Both result in constitutive expression of the lac operon.

A DNA segment that must be adjacent to the gene(s) it regulates is called a [] -acting element.

cis

The lacI+ allele is ______ to lacI— in ______.

dominant; trans

An cis-acting element is typically a ______.

DNA segment that can influence only the expression of adjacent genes

The product of the lacI gene is a(n) [] acting protein that can bind to the [] of a lac operon regardless of its chromosomal location.

trans; operator

Consider a bacterial cell with the genotype lacI+ o+ lacZ+ lacY— that was transformed with an F' plasmid carrying lacIs o+ lacZ— lacY+. The expression of the genes lacZ+ and lacY+ in the merodiploid bacterium is ______.

repressible in the absence or presence of lactose

The lac operon genes are transcribed together in what order?

5'-lacZ-lacY-lacA-3'

Which of the following proteins may function as a dimer or tetramer?

Lac repressor

A lacIS mutation will affect codons for amino acids in the _____.

inducer-binding domain of lacI

Mutations in trans-acting elements typically occur in ______, while mutations in cis-acting elements occur in ______.

protein-encoding genes; protein-binding sites

The helix-turn-helix motif is commonly found in _____.

DNA-binding proteins

The lac operon structural genes are transcribed as _____.

part of a single polycistronic mRNA with three independent ribosome binding sites

When purified, the Lac repressor is ______.

a dimer or a tetramer

How many domains does the Lac repressor contain?

helix-turn-helix

a transcription factor DNA-binding domain; for example, the Lac repressor is a helix-turn-helix protein, and the homeodomain of Hox proteins is a helix-turn-helix domain. The DNA-binding domain of the Lac repressor protein has a characteristic three dimensional structure

What determines the DNA binding specificity of a protein with a helix-turn-helix motif?

The sequences of amino acids in the helices

The DNase I footprinting technique is used to show where [] bind to

DNA; proteins

Because there is an overlap between the sequences of the lac [] and lac [] inding of the repressor to the DNA will inhibit RNA polymerase from binding. As a result, the expression of the lac operon genes is blocked.

operator; promoter

DNA footprinting experiments have revealed that the lac operon has a total of [] operator sites.

The positive regulator of the lac operon is the []

cAMP receptor protein

description of the positive control of the lac operon

cAMP binds CRP → cAMP-CRP complex binds to lac operon → RNA polymerase is recruited to the promoter

The small nucleotide [] (cAMP) binds to a protein called CRP, and the complex can positively regulate the lac operon.

cyclic adenosinemonophospate

The transport of glucose into a bacterial cell causes the intracellular level of cyclic-AMP to fall because the enzyme [] [] is inhibited.

adenylyl cyclase

genes in the trp operon.

trpB trpE trpC trpA trpD

The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is []

catabolite repression the repression of transcription in sugar-metabolizing operons like the lac operon when glucose or another preferred catabolite is present.

RNA leader sequence

the 5' untranslated region (5' UTR) of an mRNA.

RNA leader sequences are [] in that they can alter their stem-loop structures and thus their function in response to a wide variety of environmental cues.

allosteric

Transcription begins but terminates before the entire mRNA is made during []

attenuation

hairpin loop/stem loop

a structure formed when a single strand of RNA folds back on itself because of complementary base pairing between different regions in the same molecule. Also called a stem loop. can terminate transcription of the rest of the mRNA prematurely.

In attenuation, transcription ______.

is stopped prematurely

An RNA leader whose secondary structure, and thus its effect on gene expression, is determined by whether or not it's bound to a small molecule effector is called a(n)

riboswitch | allosteric RNA leaders that bind small molecule effectors to control gene expression.

In attenuation, the level of an amino acid governs the conformation of the leader indirectly. However, leaders that act as [] change conformation by binding a particular effector directly.

riboswitch

terminators

sequences in RNA transcripts that cause RNA polymerase to stop transcription; stem-loop structures in an RNA leader sequence that stop transcription of the RNA downstream.

Regulatory sRNAs are typically ______ nucleotides long.

50-400 nt

Regulatory RNAs that are transcribed from the opposite DNA strand to that of the mRNA are called [] RNAs

antisense

fusion gene

a gene made up of parts of two or more different genes.

The term sRNAs refers to [] RNA molecules that regulate translation in trans by base-pairing with mRNAs in bacteria.

small

reporter gene

a protein-coding region of a gene incorporated into a recombinant DNA molecule along with putative DNA regulatory elements. After transformation of bacteria or incorporation of the reporter gene into the genome of an organism, the reporter gene “reports” the activity of the putative regulatory elements by expressing the protein.

The lac operon control region can help produce protein drugs in bacteria. The first step in this process is the creation of a recombinant plasmid in which the lac regulatory region is fused to the []encoding the protein to be expressed.

ORF

The entire set of RNAs produced by a cell is called its ______.

transcriptome

Scientists are currently exploring the possibility of targeting the quorum-sensing mechanism of pathogenic bacteria in the development of new antibiotics. What are advantages of this approach?

Quorum-sensing proteins do not resemble any human proteins. It might be more difficult for bacteria to develop resistance to such drugs.