Q: A researcher is comparing the DNA base composition of two bacterial species. Which formula would they use to determine the GC content?

$$GC\% = \frac{G + C}{A + T + G + C} \times 100$$

Question 1

Which of the following best describes the difference between taxonomy and phylogeny in microbiology?

Accepted Answer

Taxonomy is the classification of organisms based on similarities, while phylogeny is the study of their evolutionary history.

Question 2

A bacterium is found thriving in a hot spring at 80°C. According to the global distribution chart, which category does this organism most likely belong to?

Accepted Answer

Thermophile

Question 3

Which method would be most appropriate for distinguishing between two Gram-negative bacterial species in a clinical sample?

Accepted Answer

Biochemical tests

Question 4

A scientist uses mass spectrophotometry to identify cellular proteins in a bacterial sample. What is the main advantage of this method?

Accepted Answer

It provides a unique protein profile that can be matched to a database.

Question 5

Which of the following statements about viruses is TRUE according to the three domain system?

Accepted Answer

Viruses are not part of the three domain system.

Question 6

A sample of unknown bacteria is mixed with antibodies specific to known bacterial species. Clumping is observed. What does this indicate?

Accepted Answer

The bacteria are specific for the type of antibody used.

Question 7

Which of the following is a key feature of the three domain system developed by Woese in 1978?

Accepted Answer

Classification based on ribosomal RNA (rRNA) nucleotide sequences.

Question 8

Which of the following best describes a prokaryotic species?

Accepted Answer

A population of cells within similar characteristics.

Question 9

Which of the following is NOT a method used to classify and identify microorganisms?

Accepted Answer

Measuring atmospheric pressure

Question 10

A Gram stain is performed on a bacterial sample. What does a positive Gram stain indicate about the cell wall?

Accepted Answer

The cell wall contains a thick peptidoglycan layer.

Question 11

Which of the following tests is most specific for detecting antibodies against a particular infection?

Accepted Answer

Western blotting

Question 12

A researcher is comparing the DNA base composition of two bacterial species. Which formula would they use to determine the GC content?

Accepted Answer

$$GC\% = \frac{G + C}{A + T + G + C} 	imes 100$$

Question 13

Which of the following statements about dichotomous keys and cladograms is correct?

Accepted Answer

Dichotomous keys help identify organisms in their natural world; cladograms show evolutionary relationships among organisms.

Question 14

Which of the following is a real-world application of enzyme-linked immunosorbent assay (ELISA)?

Accepted Answer

Detection of antigens or antibodies in a sample, such as HIV or pregnancy tests

Question 15

A scientist is using DNA fingerprinting to compare genetic fragments from different organisms. What is the main purpose of this technique?

Accepted Answer

To provide information on genetic similarities and differences

Question 16

Which of the following statements about the evolutionary history of organisms is supported by phylogenetic trees?

Accepted Answer

Groups of organisms evolved from a common ancestor.

Question 17

Which of the following is TRUE regarding the identification of microorganisms using serology?

Accepted Answer

Serology analyzes blood serum for antibodies produced in response to microorganisms.

Question 18

A clinical lab uses MALDI-TOF to identify a bacterial pathogen. What does MALDI-TOF analyze to determine the identity of the organism?

Accepted Answer

The unique proteomic fingerprint of the organism

Question 19

Which of the following is a correct statement about the classification of organisms according to the modern three domain system?

Accepted Answer

Eukaryotes originated from the folding of prokaryotic plasma membranes.

Question 20

Which of the following is a plausible reason why rapid biochemical tests are important in clinical microbiology?

Accepted Answer

They can perform several biochemical tests simultaneously, speeding up identification.

Ch. 10

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