Nokea
A patient with a genetic mutation of BRCA1 and a family history of breast cancer is admitted to the surgical unit where she is scheduled that day for a bilateral simple mastectomy. What is the reason for this procedure?
- A. Prevent breast cancer
- B. Diagnose breast cancer
- C. Cure or control breast cancer
- D. Provide palliative care for untreated breast cancer
Correct Answer: A
Rationale: A bilateral simple mastectomy is performed to prevent breast cancer in high-risk individuals with BRCA1 mutations.
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What factor differentiates a malignant tumor from a benign tumor?
- A. It causes death
- B. It grows at a faster rate
- C. It is often encapsulated
- D. It invades and metastasizes
Correct Answer: D
Rationale: Malignant tumors invade surrounding tissues and can metastasize to distant sites, whereas benign tumors do not exhibit these characteristics.
Thymocytes undergoing positive selection express:
- A. TCR
- B. CD4
- C. CD8
- D. All of the above
Correct Answer: D
Rationale: Thymocytes undergoing positive selection express both CD4 and CD8 co-receptors along with a functional T-cell receptor (TCR). CD4 and CD8 help in recognizing MHC molecules, while TCR is crucial for antigen recognition. Positive selection ensures that thymocytes with a functional TCR that can interact with self-MHC molecules survive. Therefore, the correct answer is D, as thymocytes undergoing positive selection express TCR, CD4, and CD8. Choice A, TCR alone, is incorrect as CD4 and CD8 are also expressed. Choices B and C are incorrect as positive selection involves the expression of both CD4 and CD8, not just one or the other.
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.
Why did Barry Marshall drink a pure culture of Helicobacter pylori?
- A. To demonstrate the H. pylori is the cause of gastric cancer
- B. To demonstrate an association between H. pylori infection and gastric ulcers
- C. To demonstrate that gastric ulcers are caused by stress rather than bacterial
- D. A and B are both correct
Correct Answer: B
Rationale: Barry Marshall drank a pure culture of H. pylori to demonstrate an association between H. pylori infection and gastric ulcers. This is because he wanted to prove the theory that the bacteria is a primary cause of stomach ulcers, contradicting the prevailing belief at the time. Choice A is incorrect because the direct link between H. pylori and gastric cancer was not the primary focus of his experiment. Choice C is incorrect as his goal was to show the bacterial link to ulcers, not to disprove stress as a factor. Choice D is incorrect because only choice B accurately reflects his intended purpose.
What is the key characteristic of adaptive immunity compared to innate immunity?
- A. It uses physical barriers like skin
- B. It has antigen-specific responses and memory
- C. It responds to all antigens non-specifically
- D. It is faster than innate immunity
Correct Answer: B
Rationale: The correct answer is B because adaptive immunity is characterized by antigen-specific responses and memory. This means that it can recognize and target specific antigens upon exposure and develop long-lasting immunological memory.
Choice A is incorrect because physical barriers like skin are part of innate immunity, not adaptive immunity. Choice C is incorrect as adaptive immunity responds to specific antigens, not all antigens non-specifically. Choice D is incorrect because adaptive immunity typically takes longer to respond compared to innate immunity due to the need for activation and clonal expansion of specific immune cells.