Question 1

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 2

Which enzyme is responsible for introducing negative supercoils into DNA in most prokaryotic cells?

Accepted Answer

DNA gyrase

Question 3

A mutation in the gene encoding the sigma factor in E. coli would most directly affect which process?

Accepted Answer

The ability of RNA polymerase to recognize promoters

Question 4

Which of the following statements about plasmids is FALSE?

Accepted Answer

Plasmids are always essential for host cell survival.

Question 5

During DNA replication, which enzyme is responsible for removing RNA primers and replacing them with DNA?

Accepted Answer

DNA polymerase I

Question 6

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Multiple codons can encode the same amino acid.

Question 7

A bacterial cell is exposed to a high temperature environment. Which protein family is most likely to be upregulated to help refold denatured proteins?

Accepted Answer

Chaperones (heat shock proteins)

Question 8

Which of the following is a key difference between transcription in prokaryotes and eukaryotes?

Accepted Answer

In prokaryotes, transcription and translation are coupled; in eukaryotes, they are separated by the nuclear envelope.

Question 9

Which of the following sequences is recognized by the sigma factor during bacterial transcription initiation?

Accepted Answer

Pribnow box (−10 region, TATAAT)

Question 10

A mutation that disrupts the Shine–Dalgarno sequence in a bacterial mRNA would most likely result in:

Accepted Answer

Failure of the ribosome to bind the mRNA properly, reducing translation efficiency.

Question 11

Which of the following best describes the function of aminoacyl-tRNA synthetases?

Accepted Answer

They attach the correct amino acid to its corresponding tRNA.

Question 12

Which of the following is TRUE regarding the directionality of DNA synthesis?

Accepted Answer

DNA synthesis always proceeds in the 5′ to 3′ direction.

Question 13

Which of the following is a function of the 23S rRNA in the ribosome?

Accepted Answer

Catalyzing peptide bond formation during translation

Question 14

A researcher isolates a mutant E. coli strain that cannot seal nicks in the DNA backbone after RNA primer removal. Which enzyme is most likely defective?

Accepted Answer

DNA ligase

Question 15

Which of the following best explains why supercoiling is necessary in prokaryotic cells?

Accepted Answer

To compact the DNA so it fits within the cell

Question 16

Which of the following is a property of the lagging strand during DNA replication?

Accepted Answer

It is synthesized discontinuously in short fragments called Okazaki fragments.

Question 17

Which of the following is a real-life consequence of R plasmids in bacteria?

Accepted Answer

They can confer resistance to multiple antibiotics, complicating treatment of infections.

Question 18

Which of the following is a key feature of polycistronic mRNA in prokaryotes?

Accepted Answer

It contains multiple open reading frames, each encoding a different protein.

Question 19

Which of the following best describes the role of the Sec system in bacteria?

Accepted Answer

It exports unfolded proteins across the cytoplasmic membrane.

Question 20

A patient is infected with a pathogenic bacterium that produces a toxin only when a specific plasmid is present. Which of the following best explains this observation?

Accepted Answer

The gene encoding the toxin is located on the plasmid.

6: Molecular Information Flow and Protein Processing in Microorganisms

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