Question 1

Which enzyme is primarily responsible for introducing negative supercoils into prokaryotic DNA, and what is the energetic requirement for this process?

Accepted Answer

DNA gyrase; requires ATP hydrolysis

Question 2

In the central dogma of molecular biology, which process directly uses the genetic blueprint to synthesize polypeptides?

Accepted Answer

Translation

Question 3

A mutation causes the loss of the Shine-Dalgarno sequence in a bacterial mRNA. What is the most likely consequence?

Accepted Answer

Translation will begin at random codons

Question 4

Which of the following best describes the structure and function of a plasmid in bacteria?

Accepted Answer

A circular, double-stranded DNA molecule that replicates independently and may confer antibiotic resistance

Question 5

During DNA replication in E. coli, which enzyme removes RNA primers and replaces them with DNA?

Accepted Answer

DNA polymerase I

Question 6

A bacterial cell is exposed to high temperatures, resulting in protein denaturation. Which group of proteins is upregulated to refold these proteins?

Accepted Answer

Chaperones (heat shock proteins)

Question 7

Which of the following statements about the genetic code is correct?

Accepted Answer

The code is degenerate, meaning multiple codons can encode the same amino acid

Question 8

What is the role of the 16S rRNA in the bacterial ribosome during translation?

Accepted Answer

It holds mRNA in position and facilitates ribosome subunit association

Question 9

Which of the following best explains why DNA replication in prokaryotes is bidirectional?

Accepted Answer

Because the chromosome is circular, allowing two replication forks to proceed in opposite directions

Question 10

A mutation in the gene encoding DNA ligase would most directly affect which step of DNA replication?

Accepted Answer

Sealing nicks between Okazaki fragments on the lagging strand

Question 11

Which of the following is a function of riboswitches in gene regulation?

Accepted Answer

They change mRNA conformation in response to small molecules, affecting transcription or translation

Question 12

Which process is described by the following equation? $$	ext{Amino acid} + 	ext{ATP} ightarrow 	ext{aminoacyl-AMP} + PP_i$$

Accepted Answer

Activation of amino acid for tRNA charging

Question 13

Which of the following is true regarding operons in bacteria?

Accepted Answer

Operons allow multiple genes to be transcribed into a single polycistronic mRNA

Question 14

What is the main difference between transcription termination in bacteria that is Rho-dependent versus Rho-independent?

Accepted Answer

Rho-dependent termination requires a protein factor, while Rho-independent relies on a GC-rich sequence with an inverted repeat

Question 15

Which of the following best describes the role of aminoacyl-tRNA synthetase?

Accepted Answer

It charges tRNA with its correct amino acid, ensuring fidelity in translation

Question 16

A bacterial cell contains a plasmid with multiple antibiotic resistance genes. What is the most likely evolutionary advantage conferred by this plasmid?

Accepted Answer

Ability to survive in environments containing antibiotics

Question 17

Which of the following is a unique feature of eukaryotic mRNA processing not found in prokaryotes?

Accepted Answer

Addition of a methylated guanine cap to the 5' end

Question 18

What is the function of the Sec system in bacterial protein secretion?

Accepted Answer

Exports unfolded proteins and inserts membrane proteins

Question 19

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

Accepted Answer

It compacts the DNA to fit within the cell

Question 20

A mutation in the gene encoding the clamp loader in E. coli would most likely result in which of the following?

Accepted Answer

DNA polymerase falling off the template strand during replication

Molecular Information Flow and Protein Processing in Microbiology

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