Nokea
In humans, the embryonic phase of development extends from fertilization to the end of week __________, after which the developing infant is called a fetus.
- A. 2
- B. 6
- C. 8
- D. 12
Correct Answer: C
Rationale: The correct answer is C: 8. The embryonic phase in humans lasts until the end of week 8. During this time, the major organs and structures of the body begin to form. After week 8, the developing organism is referred to as a fetus. Choice A (2) is too early for this transition to occur, Choice B (6) is also premature, and Choice D (12) is too late as the embryonic phase ends before week 12. Therefore, the correct answer is C (8) as it accurately reflects the timeline of embryonic development in humans.
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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.
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.
Which structure in bacteria is used for attachment to surfaces?
- A. Flagella
- B. Fimbriae
- C. Pili
- D. Capsule
Correct Answer: B
Rationale: The correct answer is B: Fimbriae. Fimbriae are short, hair-like appendages on the surface of bacteria that help in attachment to surfaces. They aid in colonization and biofilm formation. Flagella (A) are used for motility. Pili (C) are longer appendages used for conjugation and adherence to other cells. Capsules (D) are protective structures that aid in evading the host immune system, not necessarily for attachment.
All statements about plasmids are correct except:
- A. Many plasmids contain genes that confer resistance to one or more antibiotics
- B. Are smaller, circular, extrachromosomal DNAs
- C. Plasmids encode essential bacteria properties
- D. Plasmids are responsible for the bacterial conjugation
Correct Answer: C
Rationale: The correct answer is C because plasmids do not encode essential bacterial properties. They are non-essential, extra-chromosomal DNA molecules that can replicate independently within bacterial cells. Plasmids mainly contain genes for antibiotic resistance, genetic transfer, and other specific functions. Choice A is correct as many plasmids do carry antibiotic resistance genes. Choice B is also accurate as plasmids are indeed smaller, circular, and exist outside the bacterial chromosome. Choice D is true as plasmids can facilitate bacterial conjugation, allowing the transfer of genetic material between bacteria.
An 18-year-old patient has developed candidiasis after the case of pneumonia treated with β-lactam antibiotic. What antimycotic agent should be prescribed?
- A. Fluconazole
- B. Streptomycin
- C. Phthalylsulfathiazole
- D. Ampicillin
Correct Answer: A
Rationale: The correct answer is A: Fluconazole.
1. Fluconazole is an antifungal agent effective against Candida species commonly causing candidiasis.
2. Streptomycin (B) is an antibiotic used for bacterial infections, not fungal.
3. Phthalylsulfathiazole (C) is an antibacterial agent, not antifungal.
4. Ampicillin (D) is a β-lactam antibiotic, which can actually contribute to fungal infections like candidiasis.