The nucleocapsid of viruses consists of

Correct Answer: B

Rationale: The correct answer is B because the nucleocapsid of viruses is composed of the genome (genetic material) and the capsid (protein coat). The genome contains the viral genetic information, while the capsid protects the genome and helps in viral attachment and entry into host cells. Choice A is incorrect because the envelope is not part of the nucleocapsid but surrounds the capsid in some viruses. Choice C is incorrect as spikes are surface proteins on the viral envelope, not part of the nucleocapsid. Choice D is also incorrect because the envelope is external to the capsid and genome in many viruses.

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a gram-negative bacterium that produces a toxin leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, not cholera. Salmonella enterica causes salmonellosis, not cholera. Clostridium perfringens is associated with food poisoning, not cholera. In summary, Vibrio cholerae is the correct answer because it is the specific bacterium known to cause cholera, while the other choices are associated with different diseases.

Correct Answer: B

Rationale: The correct answer is B: glycocalyx. The glycocalyx is a matrix formed outside the plasma membrane that consists of glycoproteins and glycolipids. It plays crucial roles in cell-cell recognition, protection, and immune response. Cytoplasm (A) is the gel-like substance inside the cell, not outside. Exoplasm (C) is not a recognized term in biology. Cell wall (D) is a rigid structure found in plant cells, not outside the plasma membrane in all cells.

Correct Answer: A

Rationale: The most probable diagnosis is A: Malaria. The patient's symptoms of periodic chills, high fever, and profuse sweating, along with living in Africa where malaria is endemic, strongly suggest malaria. The enlarged liver and spleen are consistent with malaria infection. The low erythrocyte count indicates hemolysis, a common feature of malaria. Spotted fever and sepsis do not typically present with the same pattern of symptoms and travel history as seen in this case. Haemolytic anaemia would not explain the patient's fever episodes and other symptoms. Therefore, based on the symptoms, travel history, and laboratory findings, malaria is the most likely diagnosis.

Correct Answer: A

Rationale: The correct answer is A: Synthesize proteins. Bacterial ribosomes are responsible for translating mRNA into proteins through a process called translation. Ribosomes do not generate ATP (choice B), produce DNA (choice C), or synthesize lipids (choice D). These processes are carried out by other cellular components such as mitochondria for ATP production, DNA polymerase for DNA replication, and enzymes for lipid synthesis. The primary function of bacterial ribosomes is protein synthesis, making choice A the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Yersinia pestis. Y. pestis is responsible for causing the plague, a severe infectious disease. This bacterium is transmitted via fleas from rodents to humans. It causes bubonic, septicemic, and pneumonic plague. Clostridium difficile causes gastrointestinal infections, Neisseria gonorrhoeae causes gonorrhea, and Pseudomonas aeruginosa can cause various infections but not the plague.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. This protozoan matches the description of the causative agent because it has two nuclei, four flagella, and a ventral adhesive disc. Giardia lamblia is commonly found in the duodenum and causes giardiasis. The other choices can be eliminated because Leishmania donovani causes visceral leishmaniasis, not the described symptoms. Entamoeba coli is a non-pathogenic amoeba found in the large intestine. Trypanosoma gambiense causes African trypanosomiasis and is transmitted by the tsetse fly, not matching the described characteristics.

Correct Answer: A

Rationale: The correct answer is A: cultivating on artificial media and biochemical identification. This method is appropriate for diagnosing listeriosis because it allows for the isolation and growth of Listeria species on selective media, followed by biochemical tests to confirm the identity. Serological diagnosis with ELISA (choice B) is not as specific for Listeria and may yield false positives. Choice C, serological diagnosis with agglutination hype Widal, is not typically used for listeriosis diagnosis. Cultivating in cell cultures (choice D) is not the primary method for diagnosing listeriosis as it is less specific compared to cultivating on artificial media and biochemical identification.

Correct Answer: C

Rationale: The correct answer is C: Visceral leishmaniasis. This disease is caused by the protozoan parasite Leishmania, which is transmitted by sandfly bites. The symptoms described in the question, such as enlarged liver and spleen, peripheral gland enlargement, and eathy colored skin, are characteristic of visceral leishmaniasis. Amebiasis (choice A) typically presents with gastrointestinal symptoms, Balantidiasis (choice B) is caused by a different parasite and presents with dysentery, and Lambliasis (choice D) is caused by Giardia lamblia and presents with diarrhea.