Nokea
Which scientist proposed the concept of clonal selection?
- A. Paul Ehrlich
- B. Macfarlane Burnet
- C. Louis Pasteur
- D. Elie Metchnikoff
Correct Answer: B
Rationale: The correct answer is B: Macfarlane Burnet. Burnet proposed the concept of clonal selection in the 1950s to explain how the immune system recognizes and responds to specific antigens. He suggested that lymphocytes with receptors specific to antigens undergo clonal expansion upon encountering the antigen. This hypothesis laid the groundwork for our understanding of adaptive immunity.
A: Paul Ehrlich developed the side-chain theory of antibody formation, not clonal selection.
C: Louis Pasteur is known for his work in microbiology and vaccination, not clonal selection.
D: Elie Metchnikoff is credited with discovering phagocytosis, not clonal selection.
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An essential cofactor for restriction endonuclease enzyme activity is
- A. Zn2+
- B. Mg2+
- C. Co2+
- D. Ca2+
Correct Answer: B
Rationale: The correct answer is B: Mg2+. Mg2+ is an essential cofactor for restriction endonuclease enzymes because it stabilizes the enzyme-substrate complex, promotes proper binding of the enzyme to DNA, and facilitates the catalytic activity of the enzyme. Mg2+ ions help in the coordination of the active site residues and the phosphate backbone of DNA, which is crucial for the cleavage of DNA strands. Zn2+, Co2+, and Ca2+ do not provide the necessary coordination and stabilization required for restriction endonuclease enzyme activity, making them incorrect choices.
After teaching a patient with HIV infection about using antiretroviral drugs, the nurse recognizes that further teaching is needed when the patient says
- A. I should never skip doses of my medication, even if I develop side effects.
- B. If my viral load becomes undetectable, I will no longer be able to transmit HIV to others.
- C. I should not use any over-the-counter drugs without checking with my health care provider.
- D. If I develop a constant headache that is not relieved with aspirin or acetaminophen, I should report it within 24 hours.
Correct Answer: B
Rationale: Even with an undetectable viral load, HIV can still potentially be transmitted, especially during certain activities like unprotected sex.
A hybridoma:
- A. Secretes both polyclonal and monoclonal antibodies
- B. Is generated from the fusion of two antigen-activated B cells
- C. Can live in tissue culture indefinitely
- D. All of these options describe a hybridoma
Correct Answer: C
Rationale: Step-by-step rationale:
1. Hybridoma is a cell line formed by the fusion of a B cell (producing a specific antibody) and a myeloma cell.
2. Choice C is correct because hybridomas can be immortalized and cultured indefinitely.
3. Choice A is incorrect because hybridomas produce monoclonal antibodies, not polyclonal antibodies.
4. Choice B is incorrect because hybridomas are formed from a single B cell and a myeloma cell, not two antigen-activated B cells.
5. Choice D is incorrect as only option C accurately describes a hybridoma's characteristic of indefinite tissue culture survival.
The nurse is reviewing the immune system with a patient newly diagnosed with an autoimmune disorder. What should the nurse explain as the purpose of antibodies?
- A. They destroy foreign antigens.
- B. Work on many different antigens
- C. Are specific according to blood type
- D. Attach to antigens to label them for destruction
Correct Answer: D
Rationale: The correct answer is D. Antibodies attach to antigens to label them for destruction. This is crucial in the immune response to identify and mark harmful substances for elimination. Choice A is incorrect because antibodies do not destroy antigens directly. Choice B is incorrect as antibodies are specific to particular antigens. Choice C is incorrect as blood type specificity is determined by different antigens, not antibodies.
A small molecule that combines with a specific allosteric protein so that both prevent RNA polymerase activity is called a(n):
- A. inducer
- B. repressor
- C. corepressor
- D. leader
Correct Answer: C
Rationale: The correct answer is C: corepressor. A corepressor is a small molecule that binds to an allosteric protein to inhibit its activity. In this case, the corepressor prevents RNA polymerase activity. The other choices are incorrect because:
A: Inducer activates gene expression.
B: Repressor inhibits gene expression by binding to DNA.
D: Leader is not a term related to allosteric regulation.