Nokea
Extrachromosomal carriers of the genetic information in bacteria are:
- A. Mesosomes
- B. Plasmids
- C. Ribosomes
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Plasmids. Plasmids are extrachromosomal DNA molecules found in bacteria that can replicate independently of the bacterial chromosome. They carry additional genetic information, such as antibiotic resistance genes or virulence factors. Mesosomes (choice A) are not involved in carrying genetic information; they are infoldings of the cell membrane. Ribosomes (choice C) are cellular organelles responsible for protein synthesis, not carriers of genetic information. Choice D is incorrect as plasmids are indeed extrachromosomal carriers of genetic information in bacteria.
You may also like to solve these questions
All statements of viral neutralization reaction are true except:
- A. A key component of the reaction is the complement system involvement
- B. Specific virus neutralising antibodies block the viral ability to infect cells
- C. The antibodies are titrated and two serum samples are required
- D. It is also used to identify newly isolated virus
Correct Answer: A
Rationale: Rationale:
A: Incorrect - The complement system is not directly involved in the viral neutralization reaction.
B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells.
C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing.
D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.
During fibergastroscopy a patient with ulcer disease of the stomach, the mucosal biopsy is taken from the area of an ulcer. Impression smear is prepared from biopsy material and stained by Gram method; the rest of biopsy material is tested for urease activity. Microscopy of the impression smear revealed gram- negative spiral-shaped microorganisms, urease activity test is positive. What bacteria were detected?
- A. Helicobacter pylori
- B. Campilobacter jejuni
- C. Treponema pallidum
- D. Spirilla minor
Correct Answer: A
Rationale: The correct answer is A: Helicobacter pylori.
Rationale:
1. Gram-negative spiral-shaped microorganisms match the morphology of Helicobacter pylori.
2. Positive urease activity is a characteristic feature of Helicjsonacter pylori.
3. Helicobacter pylori is specifically associated with gastric ulcers and is a common pathogen in the gastrointestinal tract.
Summary:
Choice B, Campilobacter jejuni, is a gram-negative curved bacterium but is not typically associated with gastric ulcers or urease activity. Choice C, Treponema pallidum, is a spirochete bacterium causing syphilis, which is not related to gastric ulcers. Choice D, Spirilla minor, is a generic term for spiral-shaped bacteria and is not a specific pathogen associated with gastric ulcers or urease activity.
Tularemia is caused by
- A. Francisella tularensis
- B. Bordetella pertussis
- C. Brucella suis
- D. Legionella sp.
Correct Answer: A
Rationale: Step-by-step rationale:
1. Tularemia is caused by Francisella tularensis, a highly infectious bacterium.
2. Francisella tularensis is the only pathogen specifically known to cause tularemia.
3. The other choices (Bordetella pertussis, Brucella suis, Legionella sp.) are not associated with tularemia.
4. Therefore, the correct answer is A - Francisella tularensis.
The incubation period for hepatitis B is:
- A. One week - 10 days
- B. One month - 45 days
- C. Up to 3 months
- D. Up to 6 months
Correct Answer: C
Rationale: The correct answer is C: Up to 3 months. Hepatitis B has an average incubation period of 60-90 days, which aligns with the timeframe of up to 3 months. This period refers to the time between exposure to the virus and the onset of symptoms. One week to 10 days (choice A) is too short for hepatitis B, as it typically takes longer to manifest. One month to 45 days (choice B) is also shorter than the average incubation period for hepatitis B. Up to 6 months (choice D) is too long for hepatitis B, as the virus typically shows symptoms within 3 months.
Which of the following(s) is/are the determinants of antigenicity?
- A. Chemical nature
- B. Size of the antigen
- C. Foreign origin
- D. All of these
Correct Answer: D
Rationale: The correct answer is D, as all options A, B, and C are determinants of antigenicity.
A: Chemical nature influences how the immune system recognizes antigens.
B: The size of the antigen affects its ability to be recognized by immune cells.
C: Antigens of foreign origin are more likely to trigger an immune response.
Therefore, all of these factors together play a crucial role in determining antigenicity.