The nucleocapsid of viruses consists of:

Correct Answer: C

Rationale: Step 1: The nucleocapsid is the structure containing the viral genome and the protein capsid. Step 2: The genome carries the genetic material of the virus. Step 3: The capsid is the protein coat that encloses and protects the viral genome. Step 4: Therefore, the correct answer is C: Genome and capsid. Summary: A: Capsid and spikes - Incorrect, spikes are not part of the nucleocapsid. B: Genome and envelop - Incorrect, the envelop is not part of the nucleocapsid. D: Capsid and envelope - Incorrect, the envelope is not part of the nucleocapsid.

Correct Answer: D

Rationale: The correct answer is D: BSL4. Ebola viruses are highly infectious and pose a high risk to laboratory workers. BSL4 facilities are designed to handle agents that pose a severe threat to human health and have no available vaccines or treatments. These facilities have strict guidelines for handling infectious agents, including full-body suits, negative air pressure, and decontamination processes to prevent any possible exposure. BSL1, BSL2, and BSL3 are not adequate for handling Ebola viruses due to their lower levels of containment and safety measures.

Correct Answer: B

Rationale: The main function of bacterial pili is to facilitate conjugation and adhesion. Pili are hair-like appendages on bacteria that help in cell-to-cell interactions. They play a crucial role in bacterial conjugation by allowing the transfer of genetic material between cells. Additionally, pili help bacteria adhere to surfaces or host cells, aiding in colonization and biofilm formation. Choices A and D are incorrect because protein synthesis and toxin secretion are not the primary functions of pili. Choice C is incorrect as bacterial motility is mainly mediated by flagella, not pili.

Correct Answer: B

Rationale: The correct answer is B: Staphylococcus aureus. This bacteria is known to cause skin infections and toxic shock syndrome due to its ability to produce toxins that can lead to severe symptoms. Staphylococcus aureus is commonly found on the skin and can enter the body through cuts or wounds, causing infections. Other choices are incorrect because Pseudomonas aeruginosa typically causes infections in immunocompromised individuals, Micrococcus luteus is a common skin bacterium that is not typically pathogenic, and Propionibacterium acnes is associated with acne, not skin infections or toxic shock syndrome.

Correct Answer: B

Rationale: The correct answer is B: acidic pH. The reproductive tract's acidic pH serves as a defense mechanism by creating an environment hostile to many pathogens, preventing microbial infection. The acidic pH helps to inhibit the growth and survival of harmful microorganisms. A: Alkaline pH would actually be more favorable for microbial growth as most pathogens thrive in neutral to alkaline pH environments. C: High sugar concentration can actually promote microbial growth as many pathogens feed on sugars. D: High body temperature may help in some cases, but it is not as effective as an acidic pH in preventing microbial infection in the reproductive tract.

Correct Answer: A

Rationale: Rationale: 1. Epstein-Barr virus causes infectious mononucleosis due to primary infection. 2. Certain types of cancer, such as Burkitt lymphoma and nasopharyngeal carcinoma, are associated with Epstein-Barr virus through oncogenic mechanisms. 3. Chickenpox and shingles are caused by varicella-zoster virus (HHV3). 4. Roseola infantum is caused by human herpesvirus 6 (HHV6). Summary: Choice A is correct as Epstein-Barr virus is linked to infectious mononucleosis and specific cancers. Choices B, C, and D are incorrect as they are caused by different herpesviruses.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba gingivalis. This organism matches the description provided in the question - unicellular with pseudopodia and ingested white blood cells, commonly found in dental plaque. Entamoeba gingivalis is known to inhabit the oral cavity and is associated with periodontal disease. Trichomonas vaginalis, Giardia lamblia, and Balantidium coli do not match the characteristics mentioned in the question and are not typically found in the oral cavity.

Correct Answer: C

Rationale: The correct answer is C: rotaviruses. Rotaviruses are the most common cause of infectious diarrhea in infants and children due to their highly contagious nature and ability to spread easily in childcare settings. They are known to cause severe diarrhea, vomiting, and dehydration in young children. Noroviruses (A), adenoviruses (B), and caliciviruses (D) can also cause diarrhea, but rotaviruses are specifically known for their prevalence and severity in the pediatric population. This is why C is the correct answer.

Correct Answer: A

Rationale: The correct answer is A: T-lymphocytes. Cell-mediated immunity involves the activation of T-lymphocytes, which play a crucial role in recognizing and killing infected cells. T-lymphocytes include cytotoxic T cells, helper T cells, and regulatory T cells, all of which are involved in different aspects of cell-mediated immunity. Monocytes (choice B) are a type of white blood cell involved in phagocytosis but are not the main mediators of cell-mediated immunity. B-lymphocytes (choice C) are involved in humoral immunity, producing antibodies, not cell-mediated immunity. Choice D (A+B+C) is incorrect because cell-mediated immunity is mainly mediated by T-lymphocytes.