Nokea
Which of the following lack nucleic acids?
- A. Archaea
- B. Viruses
- C. Prions
- D. Bacteria
Correct Answer: C
Rationale: The correct answer is C: Prions. Prions are infectious proteins that lack nucleic acids, such as DNA or RNA, which are essential components of all other living organisms, including Archaea, Bacteria, and Viruses. Prions are unique in their ability to cause protein misfolding and aggregation in the brain, leading to various neurodegenerative diseases. The other choices (A: Archaea, B: Viruses, D: Bacteria) all contain nucleic acids in the form of DNA or RNA, making them distinct from prions. Therefore, C is the correct answer in this case.
You may also like to solve these questions
A family has two children. The younger child is under the year. The child has developed spastic cough attacks. Similar clinical presentation was observed in the elder preschool child one month ago. The doctor suspects pertussis infection. What method enables retrospective diagnostics of this disease?
- A. Serological
- B. Biological
- C. Bacteriological
- D. Molecular biological
Correct Answer: A
Rationale: The correct answer is A: Serological. Serological testing involves analyzing blood samples for specific antibodies produced in response to the pertussis infection. This method can detect past infections by identifying the presence of antibodies against the pertussis bacteria in the blood. In this case, since the doctor suspects pertussis infection in both children, serological testing can confirm if they have been exposed to the bacteria.
Summary:
B: Biological testing does not specifically target pertussis antibodies in the blood.
C: Bacteriological testing involves culturing bacteria from samples, which may not be as sensitive for retrospective diagnosis.
D: Molecular biological testing focuses on genetic material of the bacteria, which may not provide direct evidence of past infection.
Which of the following bacteria is known for producing a neurotoxin that causes paralysis?
- A. Clostridium botulinum
- B. Clostridium perfringens
- C. Escherichia coli
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the botulinum neurotoxin, which causes paralysis by blocking the release of acetylcholine at neuromuscular junctions. Clostridium perfringens causes gas gangrene, not paralysis. Escherichia coli is associated with gastrointestinal infections, not paralysis. Staphylococcus aureus produces enterotoxins causing food poisoning, not paralysis. Therefore, Clostridium botulinum is the correct choice based on its well-known association with paralysis due to botulinum neurotoxin production.
Artificial active immunity occurs after a vaccination: injecting or taking antigens by mouth. Takes time for T and B cells to be activated but gives relatively long lasting:
- A. TRUE
- B. FALSE
- C. Both answers can be correct depending on the given situation
- D. None of the above
Correct Answer: A
Rationale: 1. Vaccination introduces antigens to stimulate immune response.
2. T and B cells are activated to produce memory cells for long-lasting protection.
3. Active immunity develops over time post-vaccination.
4. Choice A is correct as it accurately describes the process and outcomes.
5. Choice B is incorrect as it contradicts the process of active immunity.
6. Choice C is incorrect as the process of active immunity is consistent regardless of the situation.
7. Therefore, the correct answer is A as it aligns with the mechanism and characteristics of artificial active immunity.
In which phase of mitosis do the chromatids separate?
- A. Prophase
- B. Metaphase
- C. Anaphase
- D. Telophase
Correct Answer: C
Rationale: In anaphase, sister chromatids separate and move towards opposite poles of the cell. This is facilitated by the shortening of microtubules attached to the centromeres. Prophase is the phase where chromosomes condense and the nuclear envelope breaks down. Metaphase is when chromosomes align at the metaphase plate. Telophase is when the nuclear envelope reforms and chromosomes decondense. Therefore, anaphase is the correct phase for chromatid separation.
The presence of flagella in bacterial cell represents:
- A. H-antigen
- B. O-antigen
- C. K-antigen
- D. None of the above
Correct Answer: A
Rationale: The presence of flagella in a bacterial cell represents the H-antigen. Flagella are protein structures on the cell surface that play a role in bacterial motility. The H-antigen refers to the flagellar antigen, which is involved in immune responses and bacterial identification. Option A is correct because flagella are specifically associated with the H-antigen.
Summarily, choices B and C are incorrect because the O-antigen and K-antigen are associated with lipopolysaccharide and capsule antigens, respectively, not flagella. Option D is incorrect as well because the correct association is with the H-antigen.