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

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

Accepted Answer

Helicase

Question 3

Which of the following statements about DNA structure is correct?

Accepted Answer

The strands are antiparallel and held together by hydrogen bonds between bases.

Question 4

What is the function of DNA gyrase during bacterial DNA replication?

Accepted Answer

It replaces supercoils ahead of the replication fork.

Question 5

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each new DNA molecule contains one old and one new strand.

Question 6

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

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 7

Which of the following is a key difference between bacterial and eukaryotic chromosomes?

Accepted Answer

Bacterial chromosomes are circular and usually singular, while eukaryotic chromosomes are linear and multiple.

Question 8

Which of the following codons serves as the start codon for translation in most organisms?

Accepted Answer

$$\mathrm{AUG}$$

Question 9

In the context of the lac operon, what is the role of the lac repressor protein?

Accepted Answer

It binds to the operator to block transcription in the absence of lactose.

Question 10

Which of the following best describes the function of sigma factors in bacterial transcription?

Accepted Answer

They recognize specific promoter sequences to initiate transcription.

Question 11

A bacterial cell is exposed to a heat shock. Which regulatory mechanism is most likely to be activated?

Accepted Answer

Alternative sigma factors such as RpoH and RpoE will be used to transcribe heat shock genes.

Question 12

Which of the following statements about plasmids is correct?

Accepted Answer

Plasmids are extrachromosomal, usually circular DNA molecules that can carry antibiotic resistance genes.

Question 13

Which enzyme is responsible for removing RNA primers and filling in the resulting gaps during DNA replication in bacteria?

Accepted Answer

DNA polymerase I

Question 14

A mutation in the gene encoding the proofreading subunit of DNA polymerase III would most likely result in:

Accepted Answer

Higher frequency of replication errors

Question 15

Which of the following best explains the 'wobble' hypothesis in translation?

Accepted Answer

The third base of the codon can form non-standard base pairs with the anticodon, allowing one tRNA to recognize multiple codons.

Question 16

Which of the following is a real-world consequence of a mutation in the operator region of the arginine operon in E. coli?

Accepted Answer

The operon could be constitutively expressed, leading to unnecessary arginine synthesis even when arginine is abundant.

Question 17

Which of the following best describes the role of chaperone proteins in the cell?

Accepted Answer

They assist in the proper folding of newly synthesized polypeptides.

Question 18

In a scenario where a bacterium is exposed to both glucose and lactose, which regulatory system is primarily responsible for the observed diauxic growth pattern?

Accepted Answer

Catabolite repression mediated by cAMP and CRP

Question 19

Which of the following is a function of the Sec and Tat protein secretion systems in bacteria?

Accepted Answer

They transport proteins across the cytoplasmic membrane.

Question 20

Which of the following best describes the function of an operon in prokaryotic gene regulation?

Accepted Answer

A cluster of genes transcribed as a single mRNA under the control of one promoter.

Chapter Six and Seven

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