Nokea
Plaques are:
- A. clear areas in a lawn of cultured cells caused by virus infection.
- B. stained areas in a cell culture indicating cells infected by a virus.
- C. virus colonies on agar.
- D. bacterial colonies on agar.
Correct Answer: A
Rationale: Plaques are clear areas caused by virus infection in a lawn of cultured cells. This is because viruses infect cells, causing cell death and lysis, which results in clear areas. Choice B is incorrect because stained areas are not typically associated with plaques. Choices C and D are also incorrect as they refer to virus and bacterial colonies, respectively, not plaques.
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What is a defining characteristic of immunology as a scientific field?
- A. It is largely static, with few modern discoveries
- B. It is a dynamic field, continually evolving through research
- C. It exclusively studies pathogen biology
- D. It focuses solely on innate immunity
Correct Answer: B
Rationale: The correct answer is B: It is a dynamic field, continually evolving through research. Immunology is constantly evolving due to new discoveries and advancements in technology. Research in immunology leads to a deeper understanding of the immune system and its interactions with pathogens, cancer, and other diseases. This ongoing evolution is essential for the development of new treatments and vaccines.
Explanation of why other choices are incorrect:
A: It is largely static, with few modern discoveries - This is incorrect as immunology is a rapidly advancing field with numerous breakthroughs and discoveries.
C: It exclusively studies pathogen biology - This is incorrect as immunology also encompasses the study of the immune system's responses to various stimuli, not just pathogens.
D: It focuses solely on innate immunity - This is incorrect as immunology covers both innate and adaptive immunity, as well as the interactions between them.
Which of the following is the best match between antibody class and major antibody effector function?
- A. IgG: Opsonization
- B. IgA: Complement activation
- C. IgE: Antibody-dependent cell-mediated cytotoxicity
- D. IgM: Neonatal immunity
Correct Answer: A
Rationale: The correct answer is A: IgG: Opsonization. IgG antibodies are known for their role in opsonization, where they tag pathogens for phagocytosis by immune cells. This process enhances the removal of pathogens. IgA is mainly involved in mucosal immunity and not complement activation, making choice B incorrect. IgE is associated with allergic reactions and not antibody-dependent cell-mediated cytotoxicity as stated in choice C. IgM is the first antibody produced in response to an infection and plays a role in neonatal immunity, making choice D incorrect.
Individuals unable to make the J protein found in certain immunoglobulins would be expected to have frequent infections of the
- A. intestinal tract
- B. blood.
- C. liver.
- D. pancreas.
Correct Answer: A
Rationale: The correct answer is A: intestinal tract. The J protein is crucial for the proper functioning of immunoglobulins in the mucosal immune system, which plays a major role in defending against pathogens in the intestinal tract. Without the J protein, individuals would have impaired immune responses in the gut, leading to frequent infections in the intestinal tract. Choices B, C, and D are incorrect because the J protein deficiency specifically affects the mucosal immune system in the intestinal tract, not the blood, liver, or pancreas.
Which of the following DNA polymerases cleaves a DNA sequence at the direction of 5' → 3'?
- A. DNA polymerase I
- B. DNA polymerase II
- C. DNA polymerase III
- D. DNA polymerase IV
Correct Answer: A
Rationale: The correct answer is A: DNA polymerase I. DNA polymerase I has both 5' to 3' polymerase activity and 5' to 3' exonuclease activity, allowing it to cleave DNA in the 5' to 3' direction. This enzyme can remove RNA primers during DNA replication by cleaving them in the 5' to 3' direction and replace them with DNA nucleotides. DNA polymerase II, III, and IV do not have the same exonuclease activity as DNA polymerase I, so they are not capable of cleaving DNA sequences in the 5' to 3' direction like DNA polymerase I.
T cells can recognize
- A. Linear peptides
- B. The shape of antigens
- C. Buried epitopes
- D. Soluble antigens
Correct Answer: B
Rationale: The correct answer is B: The shape of antigens. T cells recognize antigens based on their shape, specifically the conformational structure of the antigen. T cell receptors interact with the surface of antigens, forming a complex based on the shape complementarity. This interaction is crucial for T cell activation and immune response.
A: Linear peptides - While T cells can recognize linear peptides presented by MHC molecules, the primary mode of recognition is through the shape of antigens.
C: Buried epitopes - T cells typically recognize epitopes displayed on the surface of antigens rather than buried within the structure.
D: Soluble antigens - T cells can recognize both soluble and membrane-bound antigens, but the key factor is the shape rather than the solubility of the antigen.