Molecular Biology 1. Which of the following steps in prokaryotic translation tak
ID: 66342 • Letter: M
Question
Molecular Biology
1. Which of the following steps in prokaryotic translation takes place first?
a. Aminoacylation of the tRNA molecule.
b. Joining of 30S and 50S ribosomal subunits into 70S ribosomes
c. Binding of mRNA to a ribosome
d. Attachment of fMet aminoacyl tRNA
e. Catalysis by RNA polymerase
2. A mutant bacterium is isolated. This bacterial strain has the characteristic of very slow, “sticky” 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. There may be mutation in the ribosomal rRNA recognizing the Shine Delgarno sequence of the message.
c. This mutant may have altered tRNA molecules, such that the codon—anticodon interaction during translation is affected.
d. These bacteria may not manufacture enough translation factors for effective translation.
e. In this mutant, the ribosomal subunits may not associate well enough for effective translation.
3. The expression of thousands of genes simultaneously is easily accomplished using which of the following techniques ?
a. siRNAs
b. Northern blotting
c. Microarrays
d. Eastern blotting
e. PAGE analysis
4. Polycistronic mRNAs encode
a. One product that it alternatively spliced
b. More than one protein
c. A single message
d. Exclusively archaeal proteins
e. None of the above.
5. The trp operon in E coli is regulated in such manner as to allow expression of the genes only when cellular levels of tryptophan are low. When tryptophan levels are adequate , the secondary structure of the mRNA halts translation. This form of regulation is known as
a. Attenuation
b. Transcriptional regulations
c. Positive regulatory control
d. Negative regulatory control
e. Repression
6. Which of the following is an example of translational regulation?
a. Protein degradation
b. DNA splicing
c. Protein folding
d. mRNA degradation
e. DNA methylation
7. A certain gene is transformed into a plant cell for potential use as a vaccine delivery system. Upon performing a Northern blot, a good deal of mRNA for the gene is produced. However , the protein for the gene is not observed. One explanation may be that the
a. Plant cell recognize and degrades the protein in the cytoplasm.
b. Plant ribosomes are not recognizing the mRNA translational initiation sites.
c. mRNA is not stable in the plant cytoplasm.
d. All of the above
e. None of the above
7. Which of the following enzymes is associated with the formation of peptide binds?
a. Peptidase
b. Aminoacyl transferase
c. Peptidyl hydrolase
d. Inteins
e. Peptide hydrolase
8. You wish to design a drug that acts against a recently identified retrovirus. Based upon what you know about retroviruses, which of the following would be the best target for specifically interrupting the viral life cycle in eukaryotic cells?
a. Primase
b. 30S ribosomal subunits
c. Reverse transcriptase
d. RNA polymerase
e. DNA
f. Polymerase
9. One reason that prokaryotic genes do not certain introns is that
a. The introns are cut out during binary fusion.
b. Due to the short time the bacterium is around as a single organism, a 5’ cap and poly(A) tail are added immediately for translation to take place.
c. Bacterial proteins are very short and not subject to mutation.
d. Translation sometimes begins before transcription has been completed because prokaryotic do not have a nucleus.
e. Integrated viral DNA is not recognized for transcription.
10. A new antibiotic is able to bind the rho(p) factor associated with some transcription processes; as result this antibiotic would affect
a. Initiation of transcription
b. Elongation of transcription
c. Binding of the RNA polymerase
d. Termination of al transcription
e. Termination of some transcription
11. The action of new drug is unknown , so you test various aspects of eukaryotic cell processes looking an effect. You notice that the survival of cells exposed to this drug is very low. Further analysis shows the some problem and mRNAs are much longer than they should be. One hypothesis is that the drug interfere with
a. Transcription termination signals.
b. Spliceosome activity
c. Ribosomes
d. Nucleoli
e. Both choices A and B
12. Of the following , which is associated with the productive of multiple mRNAs from a single gene?
a. Alternative splicing
b. Spliceosome mutations
c. Polycistronic organization
d. Gene rearrangement
e. Both choices B and C
13. A change in a single nucleotide that results in no change in the amino acid sequence of the polypeptide produced is known as a
a. Nonsense mutation
b. Silent mutation
c. Missense mutation
d. Frameshift mutation
e. None of the above
14. DNA replication is
a. Conservative
b. Dispersive
c. Semiconservative
d. Irregular
e. None of the above
15. Which enzyme is involved in proofreading during DNA replication?
a. 5’ to 3’ exonuclease
b. 3’ to 5’ exonuclease
c. 5’ to 3’ enduclease
d. 3’ to 5’ endonuclease
f. DNA polymerase
Explanation / Answer
1. B
2. C
3. C
4. B
5. D
6. E
7. C
8. C
9. D
10.
11. E
12. A
13. B
14. C
15. B
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