Question 1

Which of the following best describes the antiparallel nature of DNA strands?

Accepted Answer

One DNA strand runs 5' to 3', while the other runs 3' to 5'.

Question 2

During DNA replication, which enzyme is responsible for unwinding the double helix at the replication fork?

Accepted Answer

DNA helicase

Question 3

A mutation changes the codon $$\mathrm{UAC} ($$tyrosine) to $$\mathrm{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 4

Which of the following statements about the lac operon is TRUE?

Accepted Answer

Allolactose acts as an inducer by binding to the repressor, inactivating it.

Question 5

Which process involves the uptake of naked DNA from the environment by a competent bacterial cell?

Accepted Answer

Transformation

Question 6

A bacterium with an F plasmid can transfer genetic material to another bacterium through which process?

Accepted Answer

Conjugation

Question 7

Which of the following best describes the function of restriction enzymes in molecular cloning?

Accepted Answer

They cut DNA at specific nucleotide sequences.

Question 8

Which of the following is a correct sequence of taxonomic ranks from broadest to most specific?

Accepted Answer

Domain, Phylum, Class, Order, Family, Genus, Species

Question 9

Which of the following is an example of mutualism in human microbiota?

Accepted Answer

Escherichia coli producing vitamin K in the human gut

Question 10

A patient is diagnosed with a persistent viral infection. Which of the following best describes this type of infection?

Accepted Answer

The virus remains in the host for long periods, often with ongoing replication.

Question 11

Which of the following correctly matches a protozoan with its mode of transmission?

Accepted Answer

Plasmodium – transmitted by Anopheles mosquito

Question 12

Which of the following best describes the function of tRNA during translation?

Accepted Answer

tRNA carries amino acids to the ribosome and matches them to the mRNA codon via its anticodon.

Question 13

Which of the following is a characteristic of a negative-sense RNA virus?

Accepted Answer

It must first be transcribed into positive-sense RNA before translation.

Question 14

Which of the following best explains the difference between B-hemolysis and alpha-hemolysis on blood agar?

Accepted Answer

B-hemolysis results in complete lysis of red blood cells, producing a clear zone, while alpha-hemolysis results in partial lysis, producing a greenish zone.

Question 15

A scientist is using PCR to amplify a segment of DNA. Which of the following is the correct sequence of steps in a PCR cycle?

Accepted Answer

Denaturation, Annealing, Extension

Question 16

Which of the following statements about conjugative plasmids is correct?

Accepted Answer

They carry genes that allow for the transfer of DNA between bacteria via conjugation.

Question 17

Which of the following best describes the role of the sigma factor in bacterial transcription?

Accepted Answer

It helps RNA polymerase recognize and bind to the promoter region.

Question 18

A patient is infected with Clostridium botulinum. Which of the following best describes this organism?

Accepted Answer

It is a Gram-positive, spore-forming anaerobe.

Question 19

Which of the following is a correct example of binomial nomenclature?

Accepted Answer

Escherichia coli

Question 20

A patient presents with a tapeworm infection. Which of the following best describes the life cycle of a cestode?

Accepted Answer

Eggs are ingested, larvae develop in intermediate host, adults mature in definitive host.

Microbiology Unit 2 Exam Review – Step-by-Step Study Guidance

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