MCQ Microbiology
MCQ Mechanisms of Microbial Genetics
1. DNA does all but which of the following?
a) serves as the genetic material passed from parent to offspring
b) remains constant despite changes in environmental conditions
c) provides the instructions for the synthesis of messenger RNA
d) is read by ribosomes during the process of translation
2. According to the central dogma, which of the following represents the flow of genetic information in cells?
a) protein to DNA to RNA
b) DNA to RNA to protein
c) RNA to DNA to protein
d) DNA to protein to RNA
3. Which of the following is the enzyme that replaces the RNA nucleotides in a primer with DNA nucleotides?
a) DNA polymerase III
b) DNA polymerase I
c) primase
d) helicase
4. Which of the following is not involved in the initiation of replication?
a) ligase
b) DNA gyrase
c) single-stranded binding protein
d) primase
5. Which of the following enzymes involved in DNA replication is unique to eukaryotes?
a) helicase
b) DNA polymerase
c) ligase
d) telomerase
6. Which of the following would be synthesized using 5′-CAGTTCGGA-3′ as a template?
a) 3′-AGGCTTGAC-4′
b) 3′-TCCGAACTG-5′
c) 3′-GTCAAGCCT-5′
d) 3′-CAGTTCGGA-5′
7. During which stage of bacterial transcription is the σ subunit of the RNA polymerase involved?
a) initiation
b) elongation
c) termination
d) splicing
8. Which of the following components is involved in the initiation of transcription?
a) primer
b) origin
c) promoter
d) start codon
9. Which of the following is not a function of the 5’ cap and 3’ poly-A tail of a mature eukaryotic mRNA molecule?
a) to facilitate splicing
b) to prevent mRNA degradation
c) to aid export of the mature transcript to the cytoplasm
d) to aid ribosome binding to the transcript
10. Mature mRNA from a eukaryote would contain each of these features except which of the following?
a) exon-encoded RNA
b) intron-encoded RNA
c) 5’ cap
d) 3’ poly-A tail
11. Which of the following is the name of the three-base sequence in the mRNA that binds to a tRNA molecule?
a) P site
b) codon
c) anticodon
d) CCA binding site
12. Which component is the last to join the initiation complex during the initiation of translation?
a) the mRNA molecule
b) the small ribosomal subunit
c) the large ribosomal subunit
d) the initiator tRNA
13. During elongation in translation, to which ribosomal site does an incoming charged tRNA molecule bind?
a) A site
b) P site
c) E site
d) B site
14. Which of the following is the amino acid that appears at the N-terminus of all newly translated prokaryotic and eukaryotic polypeptides?
a) tryptophan
b) methionine
c) selenocysteine
d) glycine
15. When the ribosome reaches a nonsense codon, which of the following occurs?
a) a methionine is incorporated
b) the polypeptide is released
c) a peptide bond forms
d) the A site binds to a charged tRNA
16. Which of the following is a change in the sequence that leads to formation of a stop codon?
a) missense mutation
b) nonsense mutation
c) silent mutation
d) deletion mutation
17. The formation of pyrimidine dimers results from which of the following?
a) spontaneous errors by DNA polymerase
b) exposure to gamma radiation
c) exposure to ultraviolet radiation
d) exposure to intercalating agents
18. Which of the following is an example of a frameshift mutation?
a) a deletion of a codon
b) missense mutation
c) silent mutation
d) deletion of one nucleotide
19. Which of the following is the type of DNA repair in which thymine dimers are directly broken down by the enzyme photolyase?
a) direct repair
b) nucleotide excision repair
c) mismatch repair
d) proofreading
20. Which of the following regarding the Ames test is true?
a) It is used to identify newly formed auxotrophic mutants.
b) It is used to identify mutants with restored biosynthetic activity.
c) It is used to identify spontaneous mutants.
d) It is used to identify mutants lacking photoreactivation activity.
21. Which is the mechanism by which improper excision of a prophage from a bacterial chromosome results in packaging of bacterial genes near the integration site into a phage head?
a) conjugation
b) generalized transduction
c) specialized transduction
d) transformation
22. Which of the following refers to the uptake of naked DNA from the surrounding environment?
a) conjugation
b) generalized transduction
c) specialized transduction
d) transformation
23. The F plasmid is involved in which of the following processes?
a) conjugation
b) transduction
c) transposition
d) transformation
24. Which of the following refers to the mechanism of horizontal gene transfer naturally responsible for the spread of antibiotic resistance genes within a bacterial population?
a) conjugation
b) generalized transduction
c) specialized transduction
d) transformation
25. An operon of genes encoding enzymes in a biosynthetic pathway is likely to be which of the following?
a) inducible
b) repressible
c) constitutive
d) monocistronic
26. An operon encoding genes that are transcribed and translated continuously to provide the cell with constant intermediate levels of the protein products is said to be which of the following?
a) repressible
b) inducible
c) constitutive
d) activated
27. Which of the following conditions leads to maximal expression of the lac operon?
a) lactose present, glucose absent
b) lactose present, glucose present
c) lactose absent, glucose absent
d) lactose absent, glucose present
28. Which of the following is a type of regulation of gene expression unique to eukaryotes?
a) attenuation
b) use of alternate σ factor
c) chemical modification of histones
d) alarmones
