Question 1

Which of the following best describes the flow of genetic information in a bacterial cell according to the central dogma of molecular biology?

Accepted Answer

DNA → RNA → Protein

Question 2

During DNA replication in Escherichia coli, which enzyme is responsible for synthesizing the majority of the new DNA strand and also possesses proofreading activity?

Accepted Answer

DNA polymerase III

Question 3

Which of the following base pairs is found only in RNA and not in DNA?

Accepted Answer

A-U

Question 4

A scientist wants to demonstrate that DNA replication is semiconservative. Which experimental approach would best show this?

Accepted Answer

Using isotopically labeled nitrogen ($$^{15}N) in $$DNA and analyzing density after replication

Question 5

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The strands are anti-parallel and held together by complementary base pairing

Question 6

In transcription, which of the following is the correct direction of RNA synthesis?

Accepted Answer

5' to 3'

Question 7

Which sigma factor in Escherichia coli is primarily responsible for the transcription of genes during heat shock response?

Accepted Answer

Sigma 32 ($$\$$sigma^{32}$$)

Question 8

What is the function of the 3'–5' exonuclease activity of DNA polymerase III?

Accepted Answer

To remove mismatched nucleotides during proofreading

Question 9

Which of the following is a key difference between prokaryotic and eukaryotic mRNA processing?

Accepted Answer

Prokaryotic mRNA is polycistronic and does not undergo splicing

Question 10

Which of the following best explains the 'wobble' position in tRNA anticodon-codon pairing?

Accepted Answer

It permits flexibility at the third base of the codon, allowing one tRNA to recognize multiple codons

Question 11

A mutation causes a bacterial mRNA to lack a stop codon. What mechanism does the cell use to rescue ribosomes stalled on this mRNA?

Accepted Answer

tmRNA (transfer-messenger RNA)

Question 12

Which of the following is NOT a step in eukaryotic mRNA processing?

Accepted Answer

Addition of a Shine-Dalgarno sequence

Question 13

During translation, what is the role of aminoacyl-tRNA synthetase?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA using ATP

Question 14

Which of the following sequences is recognized by the Rho protein to terminate transcription in bacteria?

Accepted Answer

Specific DNA sequences that cause RNA polymerase to pause

Question 15

A researcher isolates a bacterial gene that is transcribed into a single mRNA encoding three different proteins. What is this type of mRNA called?

Accepted Answer

Polycistronic mRNA

Question 16

Which of the following best describes the peptide bond formation during protein synthesis?

Accepted Answer

It is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another

Question 17

Which of the following is a real-world example of a pathogenic factor secreted by bacteria using specialized secretion systems?

Accepted Answer

Cholera toxin

Question 18

In prokaryotes, transcription and translation are said to be 'coupled.' What does this mean?

Accepted Answer

Transcription and translation occur simultaneously in the cytoplasm

Question 19

Which of the following equations correctly represents the activation of an amino acid by aminoacyl-tRNA synthetase?

Accepted Answer

$$AA + ATP \rightarrow AA{-}AMP + PP_i$$

Question 20

A mutation in the gene encoding the DnaKJ complex would most likely affect which cellular process?

Accepted Answer

Protein folding and processing

Molecular Information Flow and Protein Processing in Microorganisms

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