Chapter 16 transcription and translation

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5' caps and 3' poly(A) tails of eukaryotic mRNAs _____.

protect mRNA from degradation and enhance transcription
protect mRNA from degradation and enhance translation
mark the beginning and end of introns, respectively
act as sites for the start and stop of translation, respectively

protect mRNA from degradation and enhance translation

After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes.
Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?

A translation stop codon is added at the 3' end of the pre-mRNA.
Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.
A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
Coding sequences called exons are spliced out by ribosomes.
A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.

Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.
A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

A-site
P-site
B-site
E-site

A-site

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Codons are a nearly universal language among all organisms.
The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes.
Prokaryotic codons usually contain different bases than those of eukaryotes.
Prokaryotic codons usually specify different amino acids than those of eukaryotes.

Codons are a nearly universal language among all organisms.

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). What is the function of these two regions of the promoter?

They attach the correct nucleotide triphosphate to the template DNA strand.
They bind the sigma subunit that is associated with RNA polymerase.
They separate the two DNA strands.
They signal the initiation site.

They bind the sigma subunit that is associated with RNA polymerase.

Death cap mushrooms produce a substance called alpha-amanitin. Alpha-amanitin efficiently blocks synthesis of mRNA, but not of tRNA or rRNA in eukaryotic organisms. How is that possible?

Alpha-amanitin efficiently interferes with RNA polymerase III, but not RNA polymerase I and II.
Alpha-amanitin efficiently blocks the action of one or more basic transcription factors.
Alpha-amanitin efficiently interferes with the action of RNA polymerase II, but not RNA polymerase I or III.
Alpha-amanitin efficiently interferes with the action of RNA polymerase I, but not RNA polymerase II or III.

Alpha-amanitin efficiently interferes with the action of RNA polymerase II, but not RNA polymerase I or III.

The direction of synthesis of an RNA transcript is _____.

1' —> 5'
5' —> 3'
1' —> 3'
3' —> 5'
2' —> 4

5' —> 3'

DNA does not store the information to synthesize which of the following?

Proteins
Messenger RNA
DNA
Organelles

Organelles

During RNA processing a(n) _____ is added to the 3' end of the RNA.

3' untranslated region
a long string of adenine nucleotides
5' untranslated region
coding segment
modified guanine nucleotide

a long string of adenine nucleotides

During RNA processing a(n) _____ is added to the 5' end of the RNA.

3' untranslated region
a long string of adenine nucleotides
5' untranslated region
coding segment
modified guanine nucleotide

modified guanine nucleotide

During splicing, _____ recognize and remove _____.

snRNPs that make up the spliceosome; introns
RNAs within the ribosome; exons
RNAs within the ribosome; introns
snRNPs that make up the spliceosome; exons

snRNPs that make up the spliceosome; introns

During the elongation phase of translation, individual tRNAs move through the three sites of the ribosome in which of the following sequences?

A→P→E
E→P→A
P→E→A
P→A→E

A→P→E

During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand.
For any given gene, what ultimately determines which DNA strand serves as the template strand?

the base sequence of the gene's promoter
the location along the chromosome where the double-stranded DNA unwinds
the location of specific proteins (transcription factors) that bind to the DNA
which of the two strands of DNA carries the RNA primer

the base sequence of the gene's promoter

During transcription, in what direction is (1) RNA synthesized and (2) the DNA template "read"?

(1) 5'→;3' (2) 5'→;3'
(1) 5'→3'; (2) 3'→5'
(1) 3'→;5'; (2) 3'→5'
(1) 3'→5'; (2) 5'→3'

(1) 5'→3'; (2) 3'→5'

How are RNA hairpin turns related to termination?

The hairpin turn prevents more nucleoside triphosphates from entering the active site of the enzymes, effectively shutting off the process of polymerization.
Release factors bind to sites on the hairpin turn, causing release of the RNA transcript.
A three-base repeat signals a stop sequence, and the RNA transcript is released.
The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.

The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.

How does termination of translation take place?

The poly A tail is reached.
The 5' cap is reached.
The end of the mRNA molecule is reached.
A stop codon is reached.

A stop codon is reached.

If the DNA code for a particular amino acid is AGT, then the anticodon on the tRNA would be _____.

AGU
UCA
AGT
TCA

AGU

Post-translational modifications include all of the following except _____.

addition of carbohydrates to form a glycoprotein
formation of covalent bonds between cysteine residues of the amino acid side chains
formation of hydrogen bonds among carbonyl and amino groups of the polypeptide backbone
removal of introns

removal of introns

A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA.

larger than; smaller than
the same size as; the same size as
the same size as; larger than
larger than; the same size as

larger than; the same size as

Put the following events of transcription in chronological order.
1. Sigma binds to the promoter region.
2. The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands.
3. Sigma binds to RNA polymerase.
4. Sigma is released.
5. Transcription begins.

3, 2, 1, 4, 5
2, 3, 1, 4, 5
3, 1, 2, 5, 4
2, 3, 4, 5

3, 1, 2, 5, 4

Refer to the figure. During elongation, which site in the ribosome represents the location where a codon is being read?

small subunit
A site
E site
P site

A site

Refer to the figure. The mRNA is smaller than the length of the DNA that codes for it because _____.

the regulatory regions (introns) of the gene are not transcribed
post-transcriptional modification removes the introns
post-transcriptional modification removes the exons
bases are added to the tail of the primary transcript

post-transcriptional modification removes the introns

Refer to the figure. What is the function of the ACC sequence at the 3' end?

It stabilizes the tRNA-amino acid complex.
It is the active site of this ribozyme.
It base pairs with the codon of mRNA.
It attaches to the amino acid.

It attaches to the amino acid.

Refer to the figure. What is the function of the AGU on the loop of the tRNA?

It attaches to the amino acid.
It stabilizes the tRNA-amino acid complex.
It is the active site of this ribozyme.
It base pairs with the codon of mRNA.

It base pairs with the codon of mRNA.

The RNA segments joined to one another by spliceosomes are _____.

caps
exons
snRNPs
tails
introns

exons

Spliceosomes are composed of _____.

snRNPs and other proteins
polymerases and ligases
introns and exons
the RNA transcript and protein
snRNPs and snurps

snRNPs and other proteins

Transcription begins at a promoter. What is a promoter?

A site in DNA that recruits the RNA Polymerase
Part of the RNA molecule itself
A nontranscribed sequence on the DNA
A site found on the RNA polymerase
A site where many different proteins will bind

A site in DNA that recruits the RNA Polymerase

Translation occurs in the _____.

cytoplasm
lysosome
nucleus
mitochondrion
nucleoplasm

cytoplasm

True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.

True
False

False

What could be the consequence of a mutation that changes the sequence of nucleotides in a promoter?

a change in when the corresponding gene is transcribed
a change in the amino acid sequence of the corresponding protein
a change in the base sequence of the corresponding mRNA
a change in the efficiency of translation of the corresponding mRNA

a change in when the corresponding gene is transcribed

What determines which base is to be added to an RNA strand during transcription?

The order of the chemical groups in the backbone of the RNA molecule
Base pairing between the DNA template strand and the RNA nucleotides
Base pairing between the two DNA strands
The previous base

Base pairing between the DNA template strand and the RNA nucleotides

What happens to RNA polymerase II after it has completed transcription of a gene?

It is free to bind to another promoter and begin transcription.
It joins with another RNA polymerase to carry out transcription.
It is degraded.
It begins transcribing the next gene on the chromosome.

It is free to bind to another promoter and begin transcription.

What is meant by translocation?

The two ribosomal subunits are joined in a complex.
The completed polypeptide is released from the ribosome.
The polypeptide chain grows by one amino acid.
The ribosome slides one codon down the mRNA.

The ribosome slides one codon down the mRNA.

What is recognized by an aminoacyl tRNA synthetase?

one amino acid and the set of tRNAs that is coupled to that amino acid
the nucleotides needed to synthesize a tRNA
the set of redundant codons that specifies one amino acid
one specific codon

one amino acid and the set of tRNAs that is coupled to that amino acid

What is the process called that converts the genetic information stored in DNA to an RNA copy?

Translation
Transcription
Translocation
Replication

transcription

Where does translation take place?

Golgi apparatus
Ribosome
Nucleus
Endoplasmic reticulum

Ribosome

Which molecule or reaction supplies the energy for polymerization of nucleotides in the process of transcription?

ATP only
the interaction between RNA polymerase and the promoter
the phosphate bonds in the nucleotide triphosphates that serve as substrates
the energy released when hydrogen bonds are broken as the DNA molecule is unwound

the phosphate bonds in the nucleotide triphosphates that serve as substrates

Which nucleic acid is translated to make a protein?

rRNA
mRNA
DNA
tRNA

mRNA

Which of the following is not one of the steps in initiation of translation?

binding of tRNA carrying formyl methionine to the start codon and small ribosomal subunit
recognition and binding of mRNA by the small ribosomal subunit
formation of a polypeptide bond
binding of the large ribosomal subunit to the small ribosomal subunit

formation of a polypeptide bond

Which of the following is part of a DNA molecule?

promoters
sigma
the holoenzyme
initiation factors

promoters

Which of the following occurs in prokaryotes, but not eukaryotes?

translation in the absence of a ribosome
post-transcriptional splicing
gene regulation
concurrent transcription and translation

concurrent transcription and translation

Which of the following processes is an example of a post-translational modification?

Peptide bond formation
Initiation
Elongation
Phosphorylation

Phosphorylation

Which of the following statements best describes the promoter of a protein-coding gene?

The promoter is a site at which only RNA polymerase will bind.
The promoter is part of the RNA molecule itself.
The promoter is a site found on RNA polymerase.
The promoter is a nontranscribed region of a gene.

The promoter is a nontranscribed region of a gene.

Which of the following steps occurs last in the initiation phase of translation?

A peptide bond is formed between two adjacent amino acids.
The large ribosomal subunit joins the complex.
An aminoacyl tRNA binds to the start codon.
The small subunit of the ribosome binds to the 5' cap on the mRNA.

The large ribosomal subunit joins the complex.

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?

Complementary
Identical
Covalently bound
Permanently base-paired

Complementary

Which of the following tRNA anticodons could decode the mRNA codon CAG (recall that codons are always written in the 5'→3' direction and anticodons are written in the 3'→5' direction)?

CUG only
GUU or GUC
GUC only
CUG or GUC

GUU or GUC

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?


GTTACG
CAATCG

GTTACG
CAAUGC

GTTACG
GTTACG

GTTACG
ACCGTA

GTTACG
UAACAU

GTTACG
CAAUGC

Which one of the following, if missing, would prevent transcription from starting?

5' cap
poly A tail
AUG codon
exon
None of the above.

None of the above.

Which statement is correct concerning the function(s) of the 5' cap and the 3' poly(A) tail of eukaryotic mRNAs?

The 5' cap serves as a recognition signal for the translational machinery but plays no role in stabilizing mRNA.
Neither structure has any known function.
The poly(A) tail stabilizes the mRNA, but plays no direct role in its translation to protein.
Both structures serve as recognition signals for the translational machinery and extend the life span of the mRNA.

Both structures serve as recognition signals for the translational machinery and extend the life span of the mRNA.

Why are ribonucleotide triphosphates, rather than ribonucleotides (which have one phosphate group), the monomers required for RNA synthesis in cells?

Only ribonucleotide triphosphates contain the sugar ribose.
Ribonucleotides cannot form complementary base pairs with the DNA template.
Ribonucleotide triphosphates have low potential energy, making the polymerization reaction endergonic.
Ribonucleotide triphosphates have high potential energy, making the polymerization reaction exergonic.

Ribonucleotide triphosphates have high potential energy, making the polymerization reaction exergonic.

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