microbiology an introduction tortora test bank

Correct Answer: D

Rationale: The correct answer is D, Formation of CD4+ cells. In autoimmune reactions, CD4+ cells are actually involved in the immune response. Here's the rationale: 1. CD4+ cells are helper T cells that play a crucial role in activating other immune cells in autoimmune reactions. 2. Decreased functional activity of T-suppressors (Choice A) is typical in autoimmune reactions as it leads to unchecked immune responses. 3. Loss of tolerance for T-helpers and B-lymphocytes (Choice B) is common in autoimmune reactions, where the immune system mistakenly attacks self-cells. 4. Ag released by normally isolated tissues (Choice C) is a typical mechanism in autoimmune reactions where self-antigens trigger immune responses.

Correct Answer: B

Rationale: Rationale: 1. The grain-like sediment indicates a precipitation reaction. 2. Precipitins are antibodies that cause precipitation reactions. 3. In serological diagnostics, precipitation reactions are used to detect specific antibodies. 4. Therefore, the reaction revealed in this scenario is due to the presence of precipitins. Summary: A: Bacteriolysins - These antibodies cause bacterial lysis, not precipitation. C: Antitoxins - These antibodies neutralize toxins, not involved in precipitation reactions. D: Opsonins - These antibodies enhance phagocytosis, not related to precipitation reactions.

Correct Answer: B

Rationale: The correct answer is B: FALSE. Adenoviral infections are not restricted only to the upper respiratory tract; they can also affect the gastrointestinal tract, eyes, and other organs. Adenoviruses are known to cause a wide range of illnesses beyond just respiratory infections. Therefore, option B is correct. Option A is incorrect because it states that adenoviral infections are restricted to the upper respiratory tract, which is not true. Option C is incorrect because there is no circumstance where adenoviral infections are solely limited to the upper respiratory tract. Option D is also incorrect as the correct answer is B.

Correct Answer: B

Rationale: The correct answer is B because there are two types of herpes simplex virus: HSV-1 and HSV-2. HSV-1 typically causes oral herpes, while HSV-2 usually causes genital herpes. Choice A is incorrect because there is more than one type. Choices C and D are also incorrect as there are only two types of herpes simplex virus known to infect humans.

Correct Answer: C

Rationale: The correct answer is C: circular double-stranded DNA. Bacterial genomes are typically composed of circular double-stranded DNA due to its stability and efficient replication. Circular DNA allows for continuous replication without the need for telomeres present in linear DNA (choice B). Bacteria do not typically have double-stranded RNA genomes (choice A) as RNA is more commonly found in viruses. Single-stranded DNA (choice D) is not typically the main genetic material in bacteria, as it is less stable and less efficient for information storage compared to double-stranded DNA.