Nokea
For Parvovirus B19 it is true that:
- A. Its genome consists of dsDNA
- B. Is an enveloped virus
- C. Has segmented genome
- D. There are three structural proteins
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.
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Which of the following bacteria should be handled in a Biosafety Level 2 facility?
- A. Micrococcus luteus
- B. Bacillus subtilis
- C. Salmonella
- D. Staphylococcus epidermidis
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.
A patient presented with gas gangrene. Gram-positive rods producing spores and gas were isolated from a wound sample. Identify the microorganism.
- A. Clostridium perfringens
- B. Clostridium tetani
- C. Bacillus anthracis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is known to cause gas gangrene and is a Gram-positive rod that produces spores and gas in tissue infections. Clostridium tetani causes tetanus, not gas gangrene. Bacillus anthracis causes anthrax, not gas gangrene. Staphylococcus aureus is a Gram-positive cocci and does not produce spores or gas in the context of gas gangrene. Therefore, based on the characteristics of the microorganism isolated from the wound sample, Clostridium perfringens is the most likely causative agent.
How the prepared immunofluorescence slide should be examined?
- A. Under the fluorescence microscope using x100 oil immersion objective
- B. Under light microscope using x100 oil immersion objective
- C. Using electron microscopy
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A because immunofluorescence slides are examined under a fluorescence microscope with a x100 oil immersion objective. This is because immunofluorescence relies on the detection of fluorescently labeled antibodies, which emit light when excited by a specific wavelength. Using a fluorescence microscope allows for visualization of these labeled antibodies at high magnification and resolution, enabling precise examination of cellular structures and protein localization. Choice B is incorrect as light microscopes are not suitable for visualizing fluorescence. Choice C is incorrect as electron microscopes use electrons, not light, for imaging, which is not compatible with immunofluorescence. Choice D is incorrect as there is a specific method for examining immunofluorescence slides.
Stroma is a component of:
- A. chloroplasts
- B. mitochondria
- C. mitochondria
- D. lysosomes
Correct Answer: B
Rationale: The correct answer is B: mitochondria. Stroma is a component of chloroplasts, not mitochondria. Lysosomes contain hydrolytic enzymes, not stroma. Mitochondria have an inner and outer membrane structure, with the matrix containing the stroma where important metabolic processes occur. This is where the Krebs cycle and oxidative phosphorylation take place. Stroma in chloroplasts is where photosynthesis occurs. So, the correct answer is B because stroma is a component of mitochondria, where crucial energy production processes happen.
DNA replication occurs in which phase of the cell cycle?
- A. G phase
- B. Prophase
- C. Metaphase
- D. S phase
Correct Answer: D
Rationale: The correct answer is D: S phase. During the S phase of the cell cycle, DNA replication takes place to ensure each daughter cell receives a complete set of genetic material. This phase is characterized by the synthesis of new DNA strands. In contrast, choices A, B, and C (G phase, Prophase, Metaphase) are not associated with DNA replication. The G phase is a period of cell growth, Prophase is the initial stage of mitosis, and Metaphase is when chromosomes align. Therefore, the S phase is the specific stage where DNA replication occurs, making it the correct answer.