Cells that contain a nucleus are __________ cells.

Correct Answer: B

Rationale: The correct answer is B: eukaryotic. Eukaryotic cells have a well-defined nucleus that encloses the genetic material. The nucleus is a distinguishing feature of eukaryotic cells, separating them from prokaryotic cells (choice A) which lack a nucleus. Anucleate cells (choice C) are cells that do not have a nucleus at all. Haploid cells (choice D) contain a single set of chromosomes, but this does not necessarily imply the presence of a nucleus. Therefore, the presence of a nucleus is what categorizes cells as eukaryotic.

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by this specific bacterium due to its production of cholera toxin, leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, Salmonella enterica causes salmonellosis, and Clostridium perfringens causes food poisoning, none of which present with the characteristic symptoms of cholera.

Correct Answer: D

Rationale: The correct answer is D: sanitization. Sanitization is the process of reducing the number of microorganisms on surfaces to a safe level. In restaurants, cleaning glassware and tableware aims to eliminate harmful bacteria to prevent foodborne illnesses. Degermation (A) focuses on removing germs from a specific area, sterilization (B) eliminates all microorganisms, and disinfection (C) reduces the number of pathogens but may not completely eliminate them, making them less effective choices for this context.

Correct Answer: D

Rationale: The correct answer is D, chemotherapy combined with surgical therapy. Actinomycosis is a bacterial infection that requires a combination of antibiotics to target the bacteria and surgery to remove abscesses or infected tissues. Antibiotics alone may not penetrate abscesses effectively. Waiting for self-clearance can lead to complications. Surgical treatment alone may not eradicate the infection entirely. Therefore, the most effective therapeutic plan is to combine chemotherapy to treat the infection systemically and surgery to remove localized infections.

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: 1. Parvovirus B19 is a single-stranded DNA (ssDNA) virus. 2. The prefix "parvo-" indicates small size, characteristic of ssDNA viruses. 3. ssDNA viruses replicate in the host cell by converting their ssDNA genome into double-stranded DNA (dsDNA). 4. Therefore, the correct answer is A: Its genome consists of dsDNA. Summary of why other choices are incorrect: B: Parvovirus B19 is a non-enveloped virus, making choice B incorrect. C: Parvovirus B19 has a linear ssDNA genome, not segmented, making choice C incorrect. D: Parvovirus B19 has two structural proteins - VP1 and VP2, making choice D incorrect.

Correct Answer: A

Rationale: The most probable diagnosis is A: Candidous cheilitis. Candidous cheilitis is a fungal infection caused by Candida species. In this case, the presence of mycelium on the plaques indicates a fungal infection. The symptoms of pain, burning, and grey plaques that can be easily removed leaving hyperemia are typical for Candidous cheilitis. Choice B (Exfoliative cheilitis) is characterized by scaling and peeling of the lips, not plaques with mycelium. Choice C (Leukoplakia) is a precancerous condition causing white plaques that cannot be easily removed. Choice D (Contactant allergic cheilitis) is an allergic reaction causing inflammation, not fungal plaques.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. Clostridium botulinum produces the botulinum toxin, which causes botulism. This bacteria thrives in anaerobic environments and can contaminate improperly canned foods. Clostridium tetani causes tetanus, not botulism. Staphylococcus aureus produces enterotoxins causing food poisoning, not botulism. Escherichia coli can cause food poisoning through various toxins, but not botulism. Therefore, the correct choice is Clostridium botulinum as it specifically produces the botulinum toxin responsible for botulism.

Correct Answer: C

Rationale: The correct answer is C: Salmonella. This bacterium should be handled in a Biosafety Level 2 facility due to its potential to cause disease in humans. Salmonella is a pathogenic bacterium that can cause foodborne illnesses and infections. Handling it in a Biosafety Level 2 facility ensures proper containment and protection of personnel. A: Micrococcus luteus and B: Bacillus subtilis are common environmental bacteria that do not pose significant risks to human health, so they can be safely handled in lower biosafety levels. D: Staphylococcus epidermidis is a common skin commensal bacterium that is generally not considered highly pathogenic, so it does not require Biosafety Level 2 containment.

Correct Answer: A

Rationale: Step 1: Rubella virus belongs to the Togaviridae family, which typically exhibits icosahedral symmetry. Step 2: Icosahedral symmetry refers to a structure with 20 equilateral triangular faces, which is characteristic of many viruses, including rubella. Step 3: Therefore, choice A is correct as rubella virus indeed has icosahedral type of symmetry. Summary: - Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA. - Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane. - Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface.