Nokea
Which of the following enzymes removes 5' phosphate groups thereby preventing or decreasing the self-sealing of restricted plasmid vector molecules?
- A. Calf intestinal phosphatase
- B. Pyrophosphatase
- C. Phosphohydrolase
- D. phosphate exonuclease
Correct Answer: A
Rationale: The correct answer is A: Calf intestinal phosphatase. This enzyme removes 5' phosphate groups from DNA molecules, preventing self-ligation of restricted plasmid vectors. This step is crucial in generating linearized vectors for downstream applications. Pyrophosphatase (B) hydrolyzes pyrophosphate bonds, not 5' phosphate groups. Phosphohydrolase (C) is a general term for enzymes that hydrolyze phosphoester bonds, not specific to 5' phosphate removal. Phosphate exonuclease (D) degrades nucleic acids by removing nucleotides from the 3' end, not the 5' phosphate group.
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Mucins are
- A. Produced by all epithelial cells
- B. Heavily glycosylated proteins that form a gel-like physical barrier on mucosal surfaces
- C. Natural antibiotics produced by specialized epithelial cells
- D. Found exclusively in the respiratory tract
Correct Answer: B
Rationale: Step-by-step rationale:
1. Mucins are heavily glycosylated proteins that form a gel-like barrier on mucosal surfaces.
2. This barrier helps protect the underlying tissues from pathogens and physical damage.
3. Mucins are primarily produced by goblet cells in epithelial tissues.
4. Choice B correctly describes the function and structure of mucins.
Summary:
- Choice A is incorrect because not all epithelial cells produce mucins.
- Choice C is incorrect as mucins are not natural antibiotics.
- Choice D is incorrect as mucins are present in various mucosal surfaces, not exclusively in the respiratory tract.
Avian Influenza has not so far caused a human pandemic because
- A. Avian flu causes only mild infection in humans compared to birds
- B. Avian flu recognize a variant of sialic acid found only on avian cells
- C. Avian flu recognizes a variant of sialic acid only found in deep tissues of humans
- D. Of cross-protection obtained from the annual vaccine
Correct Answer: C
Rationale: The correct answer is C because avian influenza has not caused a human pandemic due to the fact that it recognizes a variant of sialic acid only found in deep tissues of humans. This unique binding preference prevents efficient human-to-human transmission, which is crucial for a pandemic to occur. Choice A is incorrect as avian flu can cause severe illness in humans. Choice B is incorrect because avian flu recognizing a variant of sialic acid found only on avian cells would not prevent a pandemic in humans. Choice D is incorrect as there is no specific annual vaccine for avian influenza.
If a person is infected with some deadly microbes to which quick immune response is required, we need to directly inject the preformed antibodies. This type of immunisation is known as:
- A. Active Immunisation
- B. Passive immunisation
- C. Allergic immunisation
- D. No such type of immunisation exist
Correct Answer: B
Rationale: Passive immunisation involves injecting preformed antibodies to provide immediate protection against microbes. This is suitable for quick immune response in infected individuals. Active immunisation, on the other hand, stimulates the body to produce its own antibodies over time, which is not ideal for immediate protection. Allergic immunisation is unrelated to providing antibodies. There is no immunisation type of "No such type of immunisation exist."
Which pathway in the complement system is activated by immune complexes containing IgG or IgM?
- A. Alternative pathway
- B. Classical pathway
- C. Lectin pathway
- D. Terminal pathway
Correct Answer: B
Rationale: The correct answer is B: Classical pathway. This pathway is activated by immune complexes containing IgG or IgM. When these antibodies bind to antigens, they trigger the classical pathway by forming a complex that activates C1q, initiating a cascade of reactions leading to inflammation and opsonization. The alternative pathway (A) is activated by microbial surfaces, while the lectin pathway (C) is activated by mannose-binding lectin binding to carbohydrates on pathogens. The terminal pathway (D) involves the formation of the membrane attack complex.
What is a compensatory mechanism for metabolic alkalosis?
- A. Shifting of bicarbonate into cells in exchange for chloride
- B. Kidney conservation of bicarbonate and excretion of hydrogen ions
- C. Deep,rapid respirations (Kussmaul respirations) to increase CO2 excretion
- D. Decreased respiratory rate and depth to retain CO2 and kidney excretion of bicarbonate
Correct Answer: D
Rationale: To compensate for metabolic alkalosis, the body decreases respiratory rate to retain CO2 and excretes bicarbonate via kidneys.