Question 1

Release factors of translation recognize the codon
A)UUU.
B)GUA.
C)AUG.
D)UGA.
E)GGA.

Accepted Answer

Release factors recognize stop codons, and UGA is one of the three stop codons in mRNA that signal the termination of protein synthesis.

Question 2

Which of the following is NOT a prion disease?
A)tuberculosis
B)scrapie
C)mad cow disease
D)Creutzfeldt- Jacob disease

Accepted Answer

Tuberculosis is a bacterial infection, not a prion disease.

Question 3

Ribosomes that do not anchor on the surface of the rough endoplasmic reticulum during translation MOST probably
A)have a signal peptidase error.
B)are synthesizing cytoplasmic proteins.
C)do not make the appropriate anchor protein.
D)have a defect in ribosomal proteins that allow attachment to the surface.
E)all of the above

Accepted Answer

Ribosomes that do not anchor on the rough ER are typically synthesizing proteins that will remain in the cytoplasm, as they lack the signal sequence that directs them to the ER.

Question 4

In a mutant E. coli strain, there was a mutation in the malate dehydrogenase gene that resulted in a stop codon at amino acid position #14. From subcultures of this strain, a colony was obtained that was capable of making malate dehydrogenase. Your approach to examining this phenomenon should be to examine
A)the DNA and plasmids for the incorporation of a second complete copy of the malate dehydrogenase gene.
B)the DNA sequence to see if a suppresor mutation has occurred.
C)other proteins to see if other stop codons are ignored, indicating the presence of a suppresor tRNA.
D)the DNA sequence to see if a reversion has occurred.
E)all of the above

Accepted Answer

All options are valid approaches to investigate how the colony regained the ability to produce malate dehydrogenase, including checking for a second gene copy, suppressor mutations, suppressor tRNA, or a reversion mutation.

Question 5

The initial amino acid incorporated into a nascent peptide is N- formylated in
A)prokaryotic translation.
B)prokaryotic transcription.
C)eukaryotic translation.
D)both A and C
E)both B and C

Accepted Answer

In prokaryotic translation, the initial amino acid methionine is modified to N-formylmethionine (fMet) before being incorporated into the nascent peptide chain. This modification does not occur in eukaryotic translation.

Question 6

Shine- Delgarno sequences are present in mRNAs of
A)prokaryotes.
B)algae.
C)mosses.
D)eukaryotes.
E)fungi.

Accepted Answer

Shine-Dalgarno sequences are ribosomal binding sites in the mRNA of prokaryotes, facilitating the initiation of translation.

Question 7

Ribosomes are very old structures, found in all organisms (except viruses)from bacteria to humans. As a result, molecular taxonomists are looking at relationships based upon which rRNA sequence(s)?
A)16S
B)18S
C)30S
D)both A and B
E)all of the above

Accepted Answer

Molecular taxonomists use both 16S rRNA (found in prokaryotes) and 18S rRNA (found in eukaryotes) sequences to study evolutionary relationships because these sequences are highly conserved and present in all organisms except viruses.

Question 8

AUG is the "start" codon in
A)eukaryotic translation.
B)prokaryotic translation.
C)prokaryotic modification.
D)both prokaryotic and eukaryotic translation.
E)neither prokaryotic nor eukaryotic translation.

Accepted Answer

AUG is the start codon for translation in both prokaryotic and eukaryotic organisms, signaling the beginning of protein synthesis.

Question 9

A mutant bacterium is isolated. This bacterial strain has the characteristic of very slow, "sickly" growth. You isolate mRNA from this bacteria to use in an in vitro translation system and note that even in vitro it is difficult to use this message and obtain protein. Of the following, which is a likely explanation for these results?
A)There may be a mutation in the Shine Delgarno sequence of the DNA, resulting in a RNA that poorly binds the ribosome.
B)These bacteria may not manufacture enough translation factors for effective translation.
C)This mutant may have altered tRNA molecules, such that the codon- anticodon interaction during translation is affected.
D)There may be a mutation in the ribosomal rRNA recognizing the Shine Delgarno sequence of the message.
E)In this mutant, the ribosomal subunits may not associate well enough for effective translation.

Accepted Answer

The Shine-Dalgarno sequence is crucial for ribosome binding in prokaryotes. A mutation here would affect mRNA translation both in vivo and in vitro, explaining the poor protein synthesis observed.

Question 10

When one portion of a chromosome becomes physically part of another chromosome, the type of mutation is referred to as a(n)
A)duplication.
B)nonstop.
C)inversion.
D)translocation.
E)nonsense.

Accepted Answer

Translocation is a type of chromosomal mutation where a segment of one chromosome becomes attached to another chromosome.

Question 11

In studying an E. coli strain containing a known frameshift mutation, you isolate a mutant in which this frameshift is suppressed. You therefore expect to find which of the following associated with the suppression? (Assume the frameshift has not been corrected in the coding for the peptide.)
A)suppressor tRNAs encode an amino acid for a stop signal
B)suppressor tRNAs encode a four- nucleotide anticodon
C)suppressor tRNAs encode a two- nucleotide anticodon
D)both B and C
E)all of the above

Accepted Answer

The suppressor tRNA must have an anticodon that can read the frameshifted mRNA. This requires either a four-nucleotide anticodon or a two-nucleotide anticodon that can wobble.

Question 12

With regard to translation in prokaryotes, the gene products are often encoded on polycistronic mRNAs. As a result, the quantities of each of the proteins are often graded, such that the first gene has a great deal of protein translated, whereas the last gene has very little. Which of the following features of prokaryotic translation may account for increased production of some products and decreased production of others?
A)The different messages have sequences with more or less homology to the Shine Delgarno sequence; fewer ribosomes binding results in less product.
B)There is no termination sequence at the end of each gene, so one long protein is made, resulting in equal amounts of products.
C)Feedback regulation of ribosomes tells the cell that enough product is made, and ribosomes from such mRNAs dissociate.
D)Because transcription and translation in prokaryotes are essentially coupled, there is no gradation in the amount of individual proteins made from a polycistronic message.
E)all of the above

Accepted Answer

The Shine-Dalgarno sequence is a ribosomal binding site in prokaryotic mRNA. Variations in its sequence can affect ribosome binding efficiency, leading to differences in translation initiation and thus varying amounts of protein production from different genes on a polycistronic mRNA.

Question 13

The mRNA is translated in the 3' to 5' direction in
A)archaea.
B)prokaryotes.
C)eukaryotes.
D)all of the above
E)none of the above

Accepted Answer

mRNA is translated in the 5' to 3' direction in all organisms, including archaea, prokaryotes, and eukaryotes.

Question 14

Polycistronic mRNAs encode
A)more than one protein.
B)exclusively archaeal proteins.
C)one product that it alternatively spliced.
D)a single message.
E)none of the above

Accepted Answer

Polycistronic mRNAs contain multiple open reading frames, allowing them to encode more than one protein, typically found in prokaryotes like bacteria.

Question 15

Which of the following activities is NOT associated with post- translational processing?
A)glycosylation
B)addition of lipid groups
C)specific cleavage of polypeptides
D)polyadenylation
E)chaperonin activity

Accepted Answer

Polyadenylation is a process associated with RNA processing, not post-translational modification of proteins.

Question 16

Peptide bond formation is catalyzed by an RNA molecule in
A)prokaryotes.
B)eukaryotes.
C)cyanobacteria.
D)yeast only.
E)both A and B

Accepted Answer

Peptide bond formation is catalyzed by the ribosome, which contains ribosomal RNA (rRNA) that acts as a ribozyme in both prokaryotes and eukaryotes.

Question 17

Of the following steps associated with translation, which does NOT involve hydrolysis of GTP?
A)formation of the initiation complex
B)translocation of the ribosome
C)release of polypeptide
D)binding of the aminoacyl tRNA to codon at the A site
E)aminoacylation of tRNA

Accepted Answer

Aminoacylation of tRNA involves the attachment of an amino acid to tRNA, which is catalyzed by aminoacyl-tRNA synthetases and requires ATP, not GTP.

Question 18

The appropriate folding of a newly translated protein is essential, and chronic misfolding often leads to disease, especially in vertebrates. This misfolding, particularly in the case of prion diseases, may be due to a defect in
A)proteosome function.
B)translocase.
C)the enzyme foldase.
D)insertion of proper amino acids during translation.
E)chaperone activity.

Accepted Answer

Chaperones are proteins that assist in the proper folding of other proteins. Defects in chaperone activity can lead to protein misfolding, which is a characteristic of prion diseases.

Question 19

Messenger RNAs containing premature stop codons are destroyed by the mechanism
A)nonsense- mediated decay.
B)directed RNase activity.
C)error- mediated repair.
D)nonstop decay.
E)none of the above

Accepted Answer

Nonsense-mediated decay (NMD) is a surveillance pathway that degrades mRNAs containing premature stop codons to prevent the production of truncated and potentially harmful proteins.

Question 20

Which of the following requires eIFs for initiation?
A)DNA replication
B)eukaryotic translation
C)E.coli translation
D)eukaryotic transcription
E)chaperonin activity

Accepted Answer

Eukaryotic translation requires eukaryotic initiation factors (eIFs) to facilitate the assembly of the ribosome on the mRNA and the start of protein synthesis.

Quiz 22: Gene Expression: II Protein Synthesis and Sorting

Release factors of translation recognize the codon

Which of the following is NOT a prion disease?

Ribosomes that do not anchor on the surface of the rough endoplasmic reticulum during translation MOST probably

The initial amino acid incorporated into a nascent peptide is N- formylated in

Shine- Delgarno sequences are present in mRNAs of

Ribosomes are very old structures, found in all organisms (except viruses) from bacteria to humans. As a result, molecular taxonomists are looking at relationships based upon which rRNA sequence(s) ?

AUG is the "start" codon in

When one portion of a chromosome becomes physically part of another chromosome, the type of mutation is referred to as a(n)

In studying an E. coli strain containing a known frameshift mutation, you isolate a mutant in which this frameshift is suppressed. You therefore expect to find which of the following associated with the suppression? (Assume the frameshift has not been corrected in the coding for the peptide.)

The mRNA is translated in the 3' to 5' direction in

Polycistronic mRNAs encode

Which of the following activities is NOT associated with post- translational processing?

Peptide bond formation is catalyzed by an RNA molecule in

Of the following steps associated with translation, which does NOT involve hydrolysis of GTP?

The appropriate folding of a newly translated protein is essential, and chronic misfolding often leads to disease, especially in vertebrates. This misfolding, particularly in the case of prion diseases, may be due to a defect in

Messenger RNAs containing premature stop codons are destroyed by the mechanism

Which of the following requires eIFs for initiation?