Nokea
Which of these are a type of mutation?
- A. base substitution
- B. translocation
- C. insertion sequences
- D. recombination
Correct Answer: D
Rationale: The correct answer is D: recombination. Recombination is a type of mutation that involves the exchange of genetic material between two DNA molecules. This process can lead to genetic variation and evolution. Base substitution (A) is a point mutation where one base is replaced by another. Translocation (B) involves the movement of a segment of DNA to another location in the genome. Insertion sequences (C) are short segments of DNA that can move within the genome but are not considered a type of mutation. Recombination (D) is the only choice directly related to a type of mutation involving the exchange of genetic material.
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In each of the following situations identify which option has the highest risk for human immunodeficiency virus (HIV) transmission?
- A. Transmission to women OR to men during sexual intercourse
- B. Hollow-bore needle used for vascular access OR used for IM injection
- C. First 2 to 6 months of infection OR 1 year after infection
- D. Perinatal transmission from HIV-infected mothers taking antiretroviral therapy OR HIV-infected mothers using no therapy
Correct Answer: C
Rationale: During the acute phase of HIV infection (first 2-6 months), viral loads are extremely high, increasing the likelihood of transmission.
When a B-cell undergoes immunoglobulin class switching
- A. the variable region of the light chain changes, but its constant region remains the same
- B. the variable region of the light chain remains the same, but its constant region changes
- C. the variable region of the heavy chain remains the same but its constant region changes
- D. the variable region of the heavy chain changes but its constant region remains the same
Correct Answer: C
Rationale: When a B-cell undergoes immunoglobulin class switching, the variable region of the heavy chain remains the same but its constant region changes. This process allows the B-cell to produce antibodies with different effector functions while maintaining the same antigen specificity. By changing the constant region of the heavy chain, the B-cell can switch from producing IgM to IgG, IgA, or IgE antibodies. Choices A, B, and D are incorrect because they do not accurately describe the specific changes that occur during immunoglobulin class switching in B-cells.
What type of cells do natural killer (NK) cells target?
- A. Bacterial cells
- B. Virus-infected and cancerous cells
- C. Plasma cells
- D. Self-antigens
Correct Answer: B
Rationale: Natural killer (NK) cells target virus-infected and cancerous cells because they have the ability to recognize abnormal cells through activating receptors. These cells can identify changes in surface markers associated with viral infection or cancer, leading to their destruction. NK cells do not target bacterial cells (choice A), plasma cells (choice C), or self-antigens (choice D) as these are not typically recognized as threats by the immune system. NK cells play a crucial role in immune surveillance against abnormal cells, making choice B the correct answer.
Which of the following lymphoid tissues has both hematopoietic and immune functions and acts as an emergency reservoir of blood and filters the blood as well?
- A. Tonsils and adenoids
- B. Thymus gland
- C. Spleen
- D. Lymph nodes
Correct Answer: C
Rationale: The spleen has both hematopoietic and immune functions acting as a blood filter and reservoir and plays a key role in removing old or damaged red blood cells.
Which of the following is correct with respect to measles:
- A. Outbreaks of the disease have recently occurred in developed countries as a consequence of decreased vaccination rates
- B. The disease has been eradicated globally
- C. There is no effective vaccine for this disease
- D. The disease is now easily treated and has no known long-term effects
Correct Answer: A
Rationale: Rationale for Choice A: Outbreaks of measles in developed countries are due to decreased vaccination rates, leading to lower herd immunity. This is supported by data showing increasing cases in countries with vaccine hesitancy. Other choices are incorrect because B is false - measles has not been eradicated globally, C is false - there is an effective vaccine for measles, and D is false - measles can lead to severe complications and long-term effects, especially in unvaccinated individuals.