Question 1

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

Accepted Answer

Information flows from DNA to RNA to protein.

Question 2

During DNA replication in bacteria, which enzyme is responsible for synthesizing short RNA primers required for DNA polymerase to begin synthesis?

Accepted Answer

Primase

Question 3

A mutation in the gene encoding the sigma factor of RNA polymerase 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 best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so the lagging strand is synthesized discontinuously.

Question 5

In the lac operon, what is the role of allolactose?

Accepted Answer

It acts as an inducer that binds to the repressor, preventing it from binding to the operator.

Question 6

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

In eukaryotes, mRNA undergoes splicing to remove introns.

Question 7

A researcher discovers a bacterial strain that can survive sudden changes in environmental magnesium levels. Which regulatory system is most likely involved in this adaptation?

Accepted Answer

Two-component regulatory system

Question 8

Which of the following best describes the function of transfer RNA (tRNA) during translation?

Accepted Answer

tRNA delivers the correct amino acid to the ribosome by base-pairing its anticodon with the codon on mRNA.

Question 9

Which of the following equations correctly represents the number of possible codons that can be formed from four different nucleotides, given that a codon consists of three nucleotides?

Accepted Answer

$$4^3 = 64$

Question 10

A bacterial cell is exposed to both glucose and lactose. According to the concept of carbon catabolite repression (CCR), what will happen to the expression of the lac operon?

Accepted Answer

The lac operon will be repressed because glucose is present.

Question 11

Which of the following best describes the process of antigenic variation in bacteria?

Accepted Answer

Bacteria randomly switch genes on and off to alter surface proteins, helping evade the host immune response.

Question 12

Which of the following is an example of a constitutive enzyme in bacteria?

Accepted Answer

An enzyme involved in glycolysis that is always required for energy production.

Question 13

A mutation causes a repressor protein to lose its ability to bind to the operator region of an operon. What is the most likely consequence?

Accepted Answer

Transcription of the operon will occur constitutively.

Question 14

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

Accepted Answer

Multiple codons can code for the same amino acid.

Question 15

In a bioinformatics analysis, which feature would most strongly suggest that a stretch of DNA is an open reading frame (ORF) likely to encode a protein?

Accepted Answer

It contains a start codon, a stop codon, and is longer than 300 base pairs.

Question 16

Which of the following is a real-world application of metagenomics?

Accepted Answer

Studying the total microbial genomes in ocean water to discover new antibiotics.

Question 17

Which of the following best describes the function of the enzyme DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments by forming covalent bonds between adjacent nucleotides.

Question 18

A mutation in the gene encoding the lactose transporter in E. coli prevents lactose from entering the cell. What is the most likely effect on the lac operon?

Accepted Answer

The lac operon will not be induced even if lactose is present in the environment.

Question 19

Which of the following best explains why rapid degradation of mRNA is important in bacterial cells?

Accepted Answer

It allows cells to quickly change the levels of protein synthesis in response to environmental changes.

Question 20

Which of the following is a key feature of RNA interference (RNAi) in eukaryotic cells?

Accepted Answer

Short RNA strands guide the RNA-induced silencing complex (RISC) to bind and destroy specific mRNA molecules.

Genetic Information and Gene Expression in Microbiology

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