Question 1

A hospital is experiencing frequent infections caused by bacteria that form biofilms on catheters. Why are biofilms particularly problematic in this scenario?

Accepted Answer

Biofilms protect bacteria from antibiotics and immune responses, making infections more persistent.

Question 2

Which of the following best describes a chemically defined medium?

Accepted Answer

A medium in which the exact chemical composition is known.

Question 3

A microbiologist wants to isolate bacteria that can ferment lactose and distinguish them from those that cannot. Which type of medium should she use?

Accepted Answer

Differential medium

Question 4

Which phase of the bacterial growth curve is characterized by a balance between cell division and cell death, resulting in no net increase in cell number?

Accepted Answer

Stationary phase

Question 5

An obligate anaerobe is introduced into a test tube of thioglycollate broth. Where would you expect to find the majority of its growth?

Accepted Answer

At the bottom of the tube, where oxygen concentration is lowest.

Question 6

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization removes all forms of microbial life, while disinfection eliminates only vegetative pathogens.

Question 7

A new disinfectant is tested against a bacterial species with a thick peptidoglycan layer and endospore-forming ability. Which characteristic is most likely to make this bacterium resistant to the disinfectant?

Accepted Answer

Ability to form endospores

Question 8

Which of the following statements about DNA replication in bacteria is correct?

Accepted Answer

DNA replication is semiconservative, meaning each daughter cell receives one old and one new strand.

Question 9

A point mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 10

Which of the following best describes horizontal gene transfer in bacteria?

Accepted Answer

Transfer of genetic material between unrelated bacteria, often via plasmids or viruses.

Question 11

A scientist uses a bacteriophage to transfer DNA from one bacterium to another. This process is known as:

Accepted Answer

Transduction

Question 12

Which of the following statements about plasmids is correct?

Accepted Answer

Plasmids can carry genes for antibiotic resistance and can be transferred between bacteria.

Question 13

Which of the following is a key step in the polymerase chain reaction (PCR)?

Accepted Answer

Denaturation of DNA by heating, followed by annealing of primers and extension by DNA polymerase.

Question 14

A researcher wants to insert a human gene into a bacterial plasmid. Which enzyme is most useful for cutting both the human DNA and the plasmid at specific sequences?

Accepted Answer

Restriction enzyme

Question 15

Which of the following is an example of a therapeutic application of recombinant DNA technology?

Accepted Answer

Production of human insulin by genetically engineered bacteria

Question 16

Which of the following best describes the function of a vector in genetic engineering?

Accepted Answer

A vector is a DNA molecule used to carry foreign genetic material into a host cell.

Question 17

A patient is treated with a disinfectant that targets bacterial cell membranes. Which mechanism of action is most likely involved?

Accepted Answer

Disruption of plasma membrane integrity

Question 18

Which of the following is a potential ethical concern associated with biotechnology?

Accepted Answer

The accidental release of genetically modified organisms into the environment

Question 19

A mutation changes the DNA sequence from $\mathrm{ATG}$ to $\mathrm{ACG}$. If $\mathrm{ATG}$ codes for methionine and $\mathrm{ACG}$ codes for threonine, what type of mutation has occurred?

Accepted Answer

Missense mutation

Question 20

Which of the following best explains why transposons are important in microbial genetics?

Accepted Answer

They can move genes between different locations in the genome, contributing to genetic diversity.

Exam 2: Microbial Growth, Control, Genetics, and Biotechnology: Study Guide Notes

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