openstax microbiology test bank

Correct Answer: B

Rationale: The correct answer is B: Transduction. In bacterial genetics, transduction refers to the process of DNA transfer from one bacterium to another via bacteriophages. During transduction, the bacteriophage infects a bacterium, incorporating bacterial DNA into its own genome, which is then transferred to another bacterium upon infecting it. Rationale: A: Transfection is the process of introducing foreign DNA into eukaryotic cells, not bacteria. C: Induction is the process of activating gene expression in a cell. D: Infection is a general term for the invasion of pathogens into a host organism, not specific to DNA transfer via phages in bacteria.

Correct Answer: B

Rationale: The correct answer is B: Plasmids. Plasmids are extrachromosomal DNA molecules found in bacteria that can replicate independently of the bacterial chromosome. They carry additional genetic information, such as antibiotic resistance genes or virulence factors. Mesosomes (choice A) are not involved in carrying genetic information; they are infoldings of the cell membrane. Ribosomes (choice C) are cellular organelles responsible for protein synthesis, not carriers of genetic information. Choice D is incorrect as plasmids are indeed extrachromosomal carriers of genetic information in bacteria.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a flagellated protozoa that causes the sexually transmitted infection trichomoniasis. The presence of an undulating membrane in vaginal discharge samples is characteristic of Trichomonas vaginalis. Giardia lamblia causes gastrointestinal illness, not vaginal infections. Trypanosoma brucei causes African sleeping sickness transmitted by tsetse flies. Leishmania donovani causes visceral leishmaniasis transmitted by sandflies.

Correct Answer: B

Rationale: The correct answer is B: Bacillus subtilis. Bacillus subtilis is a thermophilic bacterium capable of surviving in extreme heat due to its heat-resistant spores. It forms spores when exposed to unfavorable conditions, allowing it to withstand high temperatures. Escherichia coli (A), Staphylococcus aureus (C), and Clostridium botulinum (D) are mesophilic bacteria that do not have the same heat resistance mechanisms as Bacillus subtilis, making them unable to survive in extreme heat conditions.

Correct Answer: D

Rationale: The correct answer is D because the rubella virus has icosahedral symmetry, meaning it has a spherical shape with 20 equilateral triangular faces. This symmetry is common in many viruses and allows for efficient packaging of genetic material. Choice A is incorrect because the rubella virus does have glycoprotein spikes on its surface. These spikes help the virus attach to host cells. Choice B is incorrect because the rubella virus does have an envelope derived from the host cell membrane. This envelope plays a role in viral entry into host cells. Choice C is incorrect because the rubella virus is an ssRNA virus, not ssDNA. Its genetic material is single-stranded RNA, not DNA. In summary, the rubella virus has icosahedral symmetry and possesses glycoprotein spikes, an envelope, and ssRNA genetic material, making choices A, B, and C incorrect.