Nokea
The rearrangement of B cell antigen receptor genes occurs in
- A. Germinal centres
- B. Cortical areas of lymph nodes
- C. Bone marrow
- D. All secondary lymphoid organs
Correct Answer: C
Rationale: The rearrangement of B cell antigen receptor genes occurs in the bone marrow. This process involves the assembly of variable (V), diversity (D), and joining (J) gene segments to generate a diverse repertoire of B cell receptors. The bone marrow provides the necessary environment for this gene rearrangement to take place, ensuring the development of functional B cells. Germinal centers and cortical areas of lymph nodes are involved in B cell activation and differentiation, not gene rearrangement. While secondary lymphoid organs support B cell activation and immune responses, they are not specifically where the gene rearrangement occurs.
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What is one of the immune system's critical functions in cancer?
- A. Promoting cell growth
- B. Fighting cancer by targeting abnormal cells
- C. Enhancing pathogen resistance
- D. Stimulating autoimmune responses
Correct Answer: B
Rationale: The correct answer is B: Fighting cancer by targeting abnormal cells. The immune system plays a crucial role in cancer by identifying and eliminating abnormal cells that can develop into tumors. This process is known as immunosurveillance. Through mechanisms like T cells and natural killer cells, the immune system can detect and destroy cancerous cells before they can grow and spread. This function is essential in preventing the development and progression of cancer.
Choices A, C, and D are incorrect:
A: Promoting cell growth - The immune system does not promote cell growth in cancer; rather, it regulates and suppresses the growth of abnormal cells.
C: Enhancing pathogen resistance - While the immune system does enhance resistance against pathogens, this is not its critical function in cancer.
D: Stimulating autoimmune responses - Autoimmune responses involve the immune system attacking healthy cells, not targeting cancerous cells.
Which antibody dominates the primary immune response?
- A. IgG
- B. IgA
- C. IgM
- D. IgE
Correct Answer: C
Rationale: The correct answer is C: IgM. During the primary immune response, IgM is the first antibody produced by the immune system in response to an antigen. IgM is efficient in agglutination and complement fixation, aiding in the elimination of pathogens. IgG is more prominent in the secondary immune response. IgA is mainly found in mucosal areas. IgE is associated with allergic reactions and parasitic infections, not the primary immune response. So, IgM dominates the primary immune response by being the initial antibody produced to combat antigens.
A 26-year-old man was adopted. What health information related to his biological parents and family will be most useful to him when he gets married (select all that apply)?
- A. Cholecystitis occurring in family members
- B. Occurrence of prostate cancer in one uncle
- C. Ages of family members diagnosed with diseases
- D. Kidney stones present in extended family members
Correct Answer: C
Rationale: Information about specific diseases like prostate cancer, ages of diagnosis, and causes of death provide critical insights into potential hereditary risks, making them highly relevant for future health planning.
Hfr strains of bacteria:
- A. do not have an 'F' (fertility) factor.
- B. have an 'F' factor plasmid.
- C. have an 'F' factor integrated in the bacterial chromosome.
- D. transfer the genetic information to other bacteria with ow frequency.
Correct Answer: C
Rationale: The correct answer is C because Hfr strains of bacteria have the F factor integrated into their bacterial chromosome. This integration allows for the transfer of genetic material during conjugation. This integration results in a high frequency of genetic information transfer to recipient cells, which is a characteristic of Hfr strains.
Choice A is incorrect because Hfr strains do have the F factor, but it is integrated into their chromosome, not absent. Choice B is incorrect because Hfr strains do not just have an F factor plasmid; it is integrated into the chromosome. Choice D is incorrect because Hfr strains actually transfer genetic information with high frequency, not low frequency.
Which of the following concerned with Leishmania is NOT true
- A. Meditated by IgE
- B. Is a unicellular parasite
- C. Activation of macrophages is essential for killing the parasite
- D. Escapes host immune attack by hiding inside neutrophils
Correct Answer: a
Rationale: The correct answer is A: Mediated by IgE. Leishmania infection is not primarily mediated by IgE antibodies. The immune response against Leishmania involves T cells, macrophages, and cytokines. IgE is not a major player in the defense against Leishmania. Choices B, C, and D are incorrect because Leishmania is indeed a unicellular parasite, activation of macrophages is essential for killing the parasite, and Leishmania can hide inside neutrophils to escape the host immune attack.