Deck 22: Gene Expression: II Protein Synthesis and Sorting

Question 1

Release factors of translation recognize the codon

A)UUU.
B)GUA.
C)AUG.
D)UGA.
E)GGA.

Answer 1

D

Question 2

Which of the following is NOT a prion disease?

A)tuberculosis
B)scrapie
C)mad cow disease
D)Creutzfeldt- Jacob disease

Answer 2

A

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

Answer 3

B

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

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

Question 6

Shine- Delgarno sequences are present in mRNAs of

A)prokaryotes.
B)algae.
C)mosses.
D)eukaryotes.
E)fungi.

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

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.

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.

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.

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

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

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

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

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

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

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

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.

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

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

Question 21

Which of the following statements is NOT true concerning peptidyl transferase?

A)It is associated with the large subunit of ribosomes.
B)It requires no outside source of additional energy, such as ATP.
C)It is a ribozyme having catalytic activity.
D)It moves the ribosome, so translation continues.
E)It catalyzes peptide bond formation.

Question 22

Of the following codons, which encodes a normal translational stop?

A)AAA
B)UAG
C)AUG
D)UUU
E)AGG

Question 23

All of the following are associated with a protein folding disease EXCEPT

A)amyloid plaques.
B)apoplipoprotein E.
C)tau protein.
D)prions.
E)E- cadherin.

Question 24

The enzymes link amino acids with their appropriate tRNAs.

Question 25

In working with a potentially new antibiotic, you are attempting to determine where in prokaryotic translation this antibiotic has its effect. You have determined thus far that it interacts with a translational factor, but need to identify which one. If this antibiotic interfered with elongation, which of the following factors could be a potential site of action?

A)IF- 3 interaction with an aminoacyl tRNA
B)EF- Tu interaction with an aminoacyl tRNA
C)EF- Tu placement of N- formyl met onto the ribosome
D)EF- Ts translocation of tRNAs from the A site to the P site
E)all of the above

Question 26

The process by which cytosolic polypeptides are transported to a target organelle is via which of the following?

A)posttranslational import
B)transportin mechanisms
C)the activity of ribosomes
D)the importin protein
E)cotranslational import

Question 27

If more than one codon specifies the same amino acid, the code is said to be

A)degenerate.
B)inverse.
C)complementary.
D)redundant.
E)ambiguous.

Question 28

Within the endoplasmic reticulum, recognizes misfolded or unassembled proteins and transports them back to the cytosol.

Question 29

Segments of polypeptides that are retained following protein splicing are called

A)inteins.
B)exons.
C)cleaved.
D)introns.
E)exteins.

Question 30

Using the techniques of genetic engineering, you design a cytoplasmic protein you want to accumulate within the ER of yeast cells. To accomplish this goal, you need to

A)incorporate radioactive amino acids into the protein.
B)incorporate appropriate DNA sequence to create signal sequences into mature peptide.
C)do nothing; all proteins go through the ER.
D)incorporate appropriateDNA sequence to create signal sequences into the mature peptide.
E)incorporate appropriate mannose- 6- phosphate groups.

Question 31

Intramolecular protein splicing results in the formation of the final protein and the

A)proteosome.
B)protease.
C)inteins.
D)all of the above
E)none of the above

Question 32

The newly arriving tRNA binds in the region of the ribosome known as the site.

Question 33

In cloning a gene, you discover that the gene product is much longer than should be observed based upon the insert you successfully cloned. What problems would result in a longer cloned sequence? How will you go about investigating your hypothesis? Would your answer change based upon the presence or absence of introns? Why or why not?

Question 34

Which of the following steps in prokaryotic translation takes place first?

A)catalysis by RNA polymerase
B)attachment of f- Met aminoacyl tRNA
C)binding of mRNA to a ribosome
D)aminoacylation of the tRNA molecule
E)joining of 30S and 50S ribosomal subunits into 70S ribsomes

Question 35

In the following gene sequence, the original sequence is ABC* DEFGH. It now reads ABC* DGFEH. The * indicates the centromere. This type of mutation is a (an)

A)inversion.
B)nonsense.
C)translocation.
D)duplication.
E)point mutation.

Question 36

The transfer of polypeptides into the ER is called because the movement across the membrane is coupled with translation.

Question 37

Messenger RNAs containing no stop codons due to a frameshift mutation are eliminated by

A)error- mediate repair.
B)directed Rnase activity.
C)nonsense- mediated decay.
D)nonstop decay.
E)none of the above

Question 38

Once an amino acid has been attached to the appropriate tRNA, the tRNA is called a(n)
and the amino acid is said to be .