Nokea
Which of the following organisms produces aflatoxin, a carcinogenic substance?
- A. Candida albicans
- B. Claviceps purpurea
- C. Aspergillus flavus
- D. Staphylococcus aureus
Correct Answer: C
Rationale: Step-by-step rationale:
1. Aspergillus flavus is a fungus known to produce aflatoxin.
2. Aflatoxin is a potent carcinogen found in contaminated food.
3. Candida albicans is a yeast species not associated with aflatoxin production.
4. Claviceps purpurea is a fungus that produces ergot alkaloids, not aflatoxin.
5. Staphylococcus aureus is a bacterium known for causing food poisoning, not aflatoxin production.
Summary: Aspergillus flavus is the correct answer as it is the organism known to produce aflatoxin, a carcinogenic substance. Other choices are incorrect as they are not associated with aflatoxin production.
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After 4 months of treatment for tuberculosis the patient began complaining of toes and fingers numbness, sensation of creeps. He was diagnosed with polyneuritis. What antituberculous drug might have caused these complications?
- A. Isoniazid
- B. Rifampicin
- C. Ciprofloxacin
- D. Sodium salt of benzylpenicillin
Correct Answer: A
Rationale: The correct answer is A: Isoniazid. Isoniazid is known to cause peripheral neuropathy as a side effect, especially with prolonged use. It can lead to symptoms such as numbness, tingling, and weakness in the toes and fingers due to its neurotoxic effects. Rifampicin (B) is less likely to cause neuropathy. Ciprofloxacin (C) is not typically associated with neuropathy. Sodium salt of benzylpenicillin (D) is an antibiotic but is not known to cause polyneuritis.
After the transfer of the F plasmid from the donor to the recipient cell..
- A. It is not possible to predict the outcome
- B. The donor cells become F
- C. The two cells become F
- D. The two cells become F+
Correct Answer: D
Rationale: After the transfer of the F plasmid from the donor to the recipient cell, the correct answer is D. This is because the F plasmid carries genes for conjugation, allowing the recipient cell to become F+ (containing the F plasmid). The donor cell remains F. Choice A is incorrect as the outcome can be predicted based on the transfer of the F plasmid. Choice B is incorrect because the donor cell does not become F after transferring the F plasmid. Choice C is incorrect as only the recipient cell becomes F+, not both cells.
For family Togaviridae is true that
- A. they have helical type of symmetry
- B. they have non-segmented (-)dsRNA
- C. they have non-segmented (+)ssRNA
- D. they are non-enveloped viruses
Correct Answer: C
Rationale: Step 1: Togaviridae is a family of viruses known to have non-segmented (+)ssRNA as their genetic material.
Step 2: The positive sense RNA means that the viral RNA can be directly translated into proteins by host machinery.
Step 3: This RNA genome acts as mRNA, allowing for immediate translation of viral proteins.
Step 4: Therefore, choice C is correct as it accurately describes the genetic nature of Togaviridae.
Summary:
- Choice A is incorrect because Togaviridae viruses do not have helical symmetry.
- Choice B is incorrect because Togaviridae viruses do not have non-segmented (-)dsRNA.
- Choice D is incorrect because Togaviridae viruses are enveloped viruses.
The phagocytosis is:
- A. Killing of bacterial cells with bactericidal antibiotics
- B. Blocking of key bacterial enzymes
- C. Active engulf and destruction of microorganisms by some host cells
- D. There is no correct answer
Correct Answer: C
Rationale: The correct answer is C because phagocytosis refers to the process where certain host cells engulf and destroy microorganisms. This is an essential mechanism of the immune system to eliminate pathogens. Choice A is incorrect because phagocytosis does not involve the use of antibiotics. Choice B is incorrect as it describes a different mechanism of action against bacteria. Choice D is incorrect because phagocytosis is a well-established biological process.
The six generally recognized types of H. Influenzae are: a,b,c,d,e and f. They are divided on the basis of their:
- A. Vi-antigen
- B. K-antigen
- C. O-antigen
- D. H-antigen
Correct Answer: B
Rationale: The correct answer is B: K-antigen. H. Influenzae types are classified based on their capsular polysaccharides, which are known as K-antigens. The K-antigen is a major virulence factor and plays a crucial role in the pathogenicity of H. Influenzae. The other options (A, C, D) are not used to classify H. Influenzae types. Vi-antigen is related to Salmonella serotyping, O-antigen is characteristic of gram-negative bacteria such as Escherichia coli and Salmonella, and H-antigen is typically associated with flagellar antigens of bacteria like Salmonella and E. coli.