USMLE Exam 2

Question 1

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Accepted Answer

bcl-2 activation

Answer

Bcl-2 is an anti-apoptotic protein whose activation or overexpression inhibits programmed cell death. This prolonged cell survival is a hallmark of many cancers, particularly follicular lymphoma, where a t(14;18) translocation leads to BCL2 overexpression. Therefore, bcl-2 activation contributes to oncogenesis by preventing the natural elimination of abnormal cells.

Question 2

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Accepted Answer

Complement (C6-C8) components

Answer

Deficiencies in the terminal complement components (C5-C9), particularly C6, C7, or C8, impair the formation of the membrane attack complex (MAC). The MAC is crucial for lysing Gram-negative bacteria, especially Neisseria species. Therefore, individuals with these deficiencies are at increased risk for recurrent Neisseria infections, such as meningococcal meningitis or gonococcal infections.

Question 3

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Accepted Answer

Rathke’s pouch

Answer

Rathke's pouch is an ectodermal invagination from the roof of the primitive oral cavity that gives rise to the anterior pituitary gland (adenohypophysis). Craniopharyngiomas are tumors that arise from remnants of Rathke's pouch. These tumors are typically suprasellar and can cause symptoms due to compression of surrounding structures like the optic chiasm or hypothalamus, often leading to endocrine dysfunction.

Question 4

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Accepted Answer

12 hours

Answer

Without specific context, 12 hours is a common interval in medicine. It often represents the dosing frequency for medications taken twice daily (BID) to maintain therapeutic levels. It can also be relevant for monitoring certain physiological parameters or for the half-life of specific substances in the body.

Question 5

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Accepted Answer

Hepatitis B virus (HBV)

Answer

Hepatitis B virus (HBV) is a well-established risk factor for hepatocellular carcinoma (HCC). Chronic HBV infection leads to persistent inflammation, hepatocyte damage, and regeneration, which increases the risk of genetic mutations and malignant transformation. The viral DNA can also integrate into the host genome, further contributing to oncogenesis.

USMLE Practice Test

USMLE Practice Test

USMLE Exam 2