Nokea
If the BCR of a developing cell has no binding affinity for self-antigens in the bone marrow the B cell will be:
- A. Clonally deleted
- B. Anergized
- C. A possible cause of autoimmunity in the periphery
- D. Allowed to mature and enter the periphery
Correct Answer: D
Rationale: The correct answer is D: Allowed to mature and enter the periphery. In this scenario, since the developing B cell has no binding affinity for self-antigens in the bone marrow, it will not undergo clonal deletion or anergy. Therefore, it will be allowed to mature and enter the periphery where it can encounter foreign antigens and participate in the immune response. Choices A and B are incorrect because clonal deletion and anergy are mechanisms used to eliminate or inactivate self-reactive B cells to prevent autoimmunity. Choice C is incorrect because a B cell without self-binding affinity is not a cause of autoimmunity in the periphery.
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To provide free water and intracellular fluid hydration for a patient with acute gastroenteritis who is NPO, the nurse would expect administration of which infusion?
- A. Dextrose 5% in water
- B. Dextrose 10% in water
- C. Lactated Ringer’s solution
- D. Dextrose 5% in normal saline (0.9%)
Correct Answer: A
Rationale: D5W provides free water without adding significant electrolytes, aiding intracellular hydration.
Kinds of innate immunity barriers are
- A. External barriers such as Skin, Secretions, Mucous membranes
- B. Internal defenses such as Inflammatory response
- C. A & B
- D. Non
Correct Answer: C
Rationale: The correct answer is C because both external barriers (Skin, Secretions, Mucous membranes) and internal defenses (Inflammatory response) are types of innate immunity. External barriers physically block pathogens from entering the body, while internal defenses involve cellular and molecular responses to eliminate pathogens. Choice A alone does not cover internal defenses, and choice B alone does not cover external barriers, making them individually incomplete. Choice D is incorrect as innate immunity does involve specific barriers and responses. Therefore, choice C is the best answer as it encompasses both types of innate immunity barriers.
The vascular instability observed in severe sepsis is caused by
- A. Systemic release of cytokines such as TNF-α and IL-1β
- B. Complement activation
- C. Release of high levels of lipid mediators
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all the choices contribute to the vascular instability observed in severe sepsis. A: Systemic release of cytokines like TNF-α and IL-1β leads to vasodilation and increased capillary permeability. B: Complement activation causes inflammation and vasodilation. C: Release of high levels of lipid mediators like prostaglandins and leukotrienes further exacerbates vasodilation and vascular permeability. Therefore, all these mechanisms combined lead to the vascular instability seen in severe sepsis.
Which of the following nucleotide triplets best represents a codon?
- A. a triplet in the same reading frame as an upstream AUG.
- B. a triplet separated spatially from other triplets.
- C. a sequence in tRNA at the 3' end.
- D. a triplet that has no corresponding amino acid.
Correct Answer: A
Rationale: The correct answer is A because a codon is a triplet of nucleotides in mRNA that corresponds to a specific amino acid during protein synthesis. To be a codon, the triplet must be in the same reading frame as the start codon (AUG) to maintain the correct reading of the genetic code. Choice B is incorrect because codons are typically consecutive in mRNA. Choice C is incorrect as tRNA sequences are not codons. Choice D is incorrect because all codons correspond to specific amino acids.
Why is smallpox considered a factor that greatly helped European explorers to defeat the Native populations of the Americas (e.g. Mexico)?
- A. When the Europeans arrived there was an ongoing smallpox epidemic in the Americas that weakened the ability of the Natives to fight back
- B. The Native populations used a form of vaccination against smallpox that was often lethal and therefore they lost more lives.
- C. Smallpox was introduced in Mexico by the European explorers therefore the Native population had no immunity to it and the disease spread rapidly
- D. Both A and B are correct
Correct Answer: C
Rationale: The correct answer is C because smallpox was indeed introduced to the Americas by European explorers, leading to devastating effects on the Native populations who had no immunity. This weakened the Natives' ability to fight back against the Europeans. Option A is incorrect as there was no ongoing smallpox epidemic in the Americas before the arrival of the Europeans. Option B is also incorrect as there is no evidence that the Native populations used a lethal form of vaccination against smallpox. Option D is incorrect as only option C accurately explains the impact of smallpox on the Native populations in relation to European conquest.