12, 13 and 14 Lecture Assignment

Which sequence of events CORRECTLY describes the initiation and elongation steps of translation in prokaryotic cells?

2, 1, 3, 4, 5

Identify the anticodon sequences for an mRNA sequence that is 5′-AUG GGC ACU CAU-3′.

3′UAC 5' - 3' CCG 5' - 3' UGA 5' - 3' GUA5′

If a DNA template strand has a sequence of 3′ TACAATGTAGCC 5′, the RNA produced from it will be which sequence?

5′AUGUUACAUCGG3'

Which mechanism is NOT used by ncRNAs to bind to other molecules?

A stem loop structure in the ncRNA binds to a specific DNA sequence.

When an aminoacyl-tRNA synthetase charges a tRNA, which molecule is released?

AMP and pyrophosphate

What molecule indirectly provides the energy for translation?

ATP

What could be a possible consequence if a structural gene's TATA box is mutated?

All of the choices are correct.

Which of the following statements describe a reason ribosomal genes are useful for comparing evolutionary relationships among organisms?

All organisms possess these genes and they can be compared with each other.

Histone deacetylase inhibitors are a class of drugs used as mood stabilizers and anti-epileptics that are also being researched for their efficacy as anti-cancer agents. Histone deacetylase inhibitors block the action of histone deacetylases, which remove acetyl groups from lysine residues in histone tails. How will blocking histone deacetylases affect gene expression in the cell?

Chromatin will become more open, and gene expression will be increased.

How does RISC recognize mRNAs for silencing?

Complementary base pairing allows the miRNA or siRNA and the mRNA to interact.

Eukaryotic DNA methylation occurs on which base?

Cytosine

Fire and Mello studied the effect of RNAs made from plasmids on gene expression in the nematode C. elegans. The results from the two experimental treatments and the control are shown below. What can be concluded from these results?

Double-stranded RNA degrades more mex-3 mRNA than antisense RNA.

A bacteria contains two copies of the lac operon; one on the bacterial chromosome and one on a plasmid. The lacO site on the chromosomal lac operon is mutated and nonfunctional, whereas the lacO site on the plasmid is functional. What is the most likely outcome for the bacterial cell when glucose is declining and lactose is present?

Expression of lac structural genes on the chromosome and plasmid will increase because the lacO site does not affect the CAP protein that activates the operon.

What is the function of the HOTAIR ncRNA?

HOTAIR acts first as a scaffold, then as a guide

If a cell's splicesomes were mutated so they no longer functioned normally, what consequences would result?

Introns would remain in the mature mRNA.

Which of the following statements about RNA polymerase in bacteria is INCORRECT?

It catalyzes the addition of nucleotides to the 5′end of a growing RNA strand.

Which of the following statements accurately describes transcription by RNA polymerase?

It is possible for one RNA polymerase to transcribe one strand of DNA in the 5' to 3' direction and another RNA polymerase to transcribe the complimentary strand of DNA in the 5' to 3' direction, producing two different transcripts

When does the small ribosomal subunit bind to the translational complex in eukaryotic cells?

It is the first component to bind to the mRNA.

The protein component of telomerase has what enzymatic function?

It makes an DNA polymer using RNA as a template.

Which amino acid would Nirenberg and Leder have found when they used the triplet UAG?

None of the answers are correct.

Why would bacteria evolve so that the presence of tryptophan inhibits its own production?

Producing the enzymes that synthesize tryptophan is metabolically expensive, so it is wasteful to make them when tryptophan levels are high and its synthesis is not necessary.

What happens when the cAMP-CAP complex binds the CAP site near the lac promoter?

RNA polymerase binds to the promoter and transcription rate increases.

________ is to transcription as ________ are to translation.

RNA polymerase; ribosomes

Events that occur during transcriptional regulation in eukaryotes include

RNA processing and export from the nucleus.

Points of control in eukaryotic gene expression include

RNA processing, translation, transcription, post-translation

What would likely result from a mutation in the promoter for lac operon structural genes that increased the number of RNA polymerase molecules that bind to the DNA?

Repression at the lacO site would not be reduced but expression would increase regardless.

What is the major difference in the termination stage of translation between prokaryotes and eukaryotes?

Ribosomal subunits dissociate in prokaryotes, but remain intact in eukaryotes. (WRONG)

Craig Mellow investigated RNA interference by injecting antisense and double-stranded RNAs into C. elegans. If the antisense and double-stranded RNAs were very similar, but not identical, to C. elegans mex-3, what would be the results of their experiment?

The C. elegans mex-3 RNA would be inhibited, but not degraded, so the embryos from worms injected with antisense and double-stranded RNA would be green.

Which of the following statements about the 5′cap and mRNA processing is TRUE?

The addition of a 5′ cap to mRNA occurs while the pre-mRNA is being made.

A mutation changes the sequence of the Cas1 gene so that Cas1 protein is no longer produced. How will this affect bacterial immunity?

The bacteria not have adaptive immunity against any second infections. The bacteria will have no defense against the first infection with any bacteriophage.

In a strain of bacteria, a mutation changes the sequence of repeat 2 in the Crispr gene (see figure). How will this affect bacterial immunity?

The bacteria will have adaptive immunity against second infection with bacteriophage A, C, and D, but not B.

Jacob, Monod, and Pardee constructed a mutant strain of E. coli that carried a lacI-gene mutation (encodes the lac repressor). Which is TRUE of this mutant strain?

The lac operon is constitutively expressed.

A scientist is studying the HOTAIR ncRNA in human cells growing in culture. She identifies a mutation in a cell line that she suspects may affect the function of HOTAIR. The mutation changes the sequence in region 2 from 5′-CUCCCUU-3′ to 5′-CUGGACG-3′ (see diagram). How will this mutation affect the function of HOTAIR?

The mutant HOTAIR will bind to different target genes than the normal HOTAIR, and it will inhibit their expression.

What is the function of the poly A tail?

The poly A tail increases mRNA stability in eukaryotes.

Which of the following statements about the mRNA start codon is INCORRECT?

The start codon is usually GGA.

Which of the following is NOT true of small effector molecules?

They can regulate gene transcription by binding to DNA.

The miR-200 class of miRNAs have what effect on human health?

They reduce tumor growth.

The lacA gene found within the lac operon encodes for galactosidase transacetylase. This enzyme attaches a(n) ________ group to lactose and lactose analogs.

acetyl

What process enables a single gene to encode two or more polypeptides that are different in their amino acid sequence?

alternative splicing

The term N-terminus refers to the presence of a(n) ________ at one of the ends of a polypeptide.

amino group

What enzyme catalyzes the attachment of amino acids to tRNA molecules?

aminoacyl-tRNA synthetase

The sequence of a short ncRNA is 5' AGCCCUAUGACGUU 3'. To what is this ncRNA likely to bind?

an mRNA that contains the sequence 3' GAUACUG 5'

The likely outcome from a mutation in the lacO site (lac Operator) of the lac operon would be

binding of a repressor protein could be hindered.

The ability of glucose to repress the lac operon depends on which effector molecules?

cAMP

A eukaryotic gene that is regulated by three activator proteins is said to be under

combinatorial control.

A genes expressed at a relatively constant level in tissues regardless of variations in the animal's condition is called a

constitutive gene.

The most common eukaryotic ribosome carries out its function in the

cytosol.

Wild type bread mold can grow in a minimal medium without supplements, while certain mutated strains can only grow in a minimal medium that is supplemented with specific intermediates found in the following metabolic pathway for arginine synthesis. See the figure below for an overview of the arginine biosynthetic pathway. A strain that can grow in minimal medium containing ornithine, citrulline, or arginine, but not in minimal medium alone would have a mutation in the gene that encodes for

enzyme 1

Wild type bread mold can grow in a minimal medium without supplements, while certain mutated strains can only grow in a minimal medium that is supplemented with specific intermediates found in the following metabolic pathway for arginine synthesis. See the figure below for an overview of the arginine biosynthetic pathway.A strain that can grow in minimal medium containing ornithine, citrulline, or arginine, but not in minimal medium alone would have a mutation in the gene that encodes for

enzyme 1.

Wild type bread mold can grow in a minimal medium without supplements, while certain mutated strains can only grow in a minimal medium that is supplemented with specific intermediates. See the figure below for an overview of the arginine biosynthetic pathway.A strain that can grow in a minimal medium containing arginine, but NOT in minimal media containing citrulline nor in minimal media containing ornithine would have a mutation in the gene that encodes for ________.

enzyme 3.

The major difference in gene regulation between prokaryotes and eukaryotes is that

eukaryotic genes are arranged individually, while prokaryotic genes are grouped into operons.

Factors that can alter the level of expression of a gene include

exposure to UV radiation. presence of a particular energy substrate. an increase in environmental temperature. an increase in salinity.

The mediator protein complex in eukaryotes

facilitates interactions between RNA polymerase II and regulatory transcription factors

A cis-effect is a form of gene regulation that can occur between two DNA segments that are not physically adjacent.

false

As part of the transcriptional unit, regulatory sequences are the sites where RNA polymerase and transcription factors bind to regulate transcription.

false

Because of the abundance of ribosomes, translation is NOT an energy costly process for the cell.

false

In eukaryotes, the 40S and 60S subunits combine to form a 100S ribosome.

false

MicroRNAs increase the rate of mRNA translation.

false

Small effector molecules directly bind the DNA they regulate.

false

Translation is a relatively slow process.

false

Unmethylated CpG islands are correlated with inactive genes.

false

What process in plants does an ncRNA called COOLAIR regulate?

flowering only after being exposed to cold temperatures

An mRNA sequence is 5′-AUG GGC ACU CAU ACU UAA-3′, where AUG is the start codon and UAA is the stop codon. How many distinct aminoacyl-tRNA synthetases are required to translate the mRNA sequence?

four

Once the lac repressor binds to the lac operator site, RNA polymerase is prevented from transcribing the

galactosidase and galactoside transacetylase genes.

An organized unit of DNA sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product is called a ________.

gene

The processes of transcription and translation are collectively known as

gene expression.

A cell's ability to control its level of gene expression is called

gene regulation

Protein(s) that play a role in initiating transcription in eukaryotes include

general transcription factors. RNA polymerase II. mediators. (partial)

How does HOTAIR exert its function?

guide scaffold

The RNA sequences of some introns found in bacteria, mitochondria, chloroplasts, and some nuclear genes fold into 3-D structures that catalyze the removal of the introns. Therefore, the intron functions as a

guide. (WRONG) spliceosome. (WRONG) enzyme. (WRONG)

What is the first step in the production of a siRNA?

infection with a virus

An ncRNA consists only of several stem loop structures. What is a likely function of this ncRNA?

inhibiting translation by binding to an mRNA (WRONG) binding to other ncRNAs and preventing them from performing their function (WRONG)

DNA methylation

inhibits transcription

Intervening sequences that are transcribed, but not translated into protein are called

introns

Certain drugs use RNA interference as a mechanism of action. What molecule would the active compounds of these drugs be composed of?

nucleic acid

The amino acids of a growing polypeptide chain are held together by what kind of bond during the elongation stage of translation?

peptide

An mRNA that contains the coding sequence for two or more structural genes is called a

polycistronic mRNA.

Transcription begins near a site in the DNA called the

promoter

What molecule(s) exhibits self-splicing?

rRNA and tRNA

What is required for ncRNAs to form stem-loop structures?

regions of complementary base-sequence

An activator is to an enhancer as a(n) ________ is to a silencer.

repressor

MicroRNAs (miRNAs)

silence the expression of specific mRNAs

Which of the following serves as the "translator" or intermediary between an mRNA codon and an amino acid?

tRNA

Which is an ncRNA that functions as a guide?

telomerase RNA component (TERC)

The RNA component of telomerase (TERC), has which function(s)?

template guide

How many nucleotides are contained in a single codon?

three

In targeting a protein to the ER lumen, the SRP RNA functions

to alter protein function as a scaffold

In E. coli cells, when lactose is absent from the environment,

trace amounts of b-galactosidase, lactose permease, and galactosidetransacetylase are made.

Which region of a structural gene contains the information that specifies an amino acid sequence?

transcribed region

What protein influences the ability of RNA polymerase to transcribe genes?

transcription factors

What is the first step in the production of a miRNA?

transcription from a nuclear gene

The event that occurs when allolactose levels increase in E. coli is

transcription of genes within the lac operon increases.

The core promoter in eukaryotes is usually composed of which two features?

transcriptional start site and TATA box

What products of nonstructural genes are never translated?

transfer RNA and ribosomal RNA

Both eukaryotes and prokaryotes require a promoter region for gene transcription.

true

Loosely packed chromatin is said to be in an open conformation.

true

RNA polymerase II of eukaryotes always requires more than one general transcription factor to initiate transcription.

true

The molecule mRNA, which contains the information to make a polypeptide, is constructed from a DNA template.

true

The termination of translation occurs when a release factor recognizes the stop codon.

true

When lactose becomes available the genes encoding b-galactosidase and lactose permease are upregulated in E. coli.

true

The molecule that functions as a corepressor for the trp operon is

tryptophan.