Basic Immune System Quizlet

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Which enzyme catalyzes the following reaction? Gap 5' - G G-A-T-C-C—3' ⋮ ⋮ ⋮ ⋮ ⋮ 3' - C-C-T-A-G G—5' Gap 5' - G-G-A-T-C-C—3' ⋮ ⋮ ⋮ ⋮ ⋮ 3' - C-C-T-A-G-G—5'

  • A. DNA ligase
  • B. DNA endonuclease
  • C. None of the options are correct
  • D. DNA polymerase 1
Correct Answer: A

Rationale: The correct answer is A: DNA ligase. DNA ligase catalyzes the joining of two DNA strands by forming a phosphodiester bond between the 3' hydroxyl of one nucleotide and the 5' phosphate of another. In the given reaction, the enzyme is needed to seal the nick in the DNA strands after the Okazaki fragments have been synthesized during DNA replication.

Explanation of other choices:
B: DNA endonuclease - Endonucleases cleave the phosphodiester bond within a polynucleotide chain, not join two DNA strands.
C: None of the options are correct - This is incorrect as DNA ligase is the correct enzyme for this reaction.
D: DNA polymerase 1 - DNA polymerase synthesizes new DNA strands by adding nucleotides to the 3' end of the growing chain, not joining two DNA strands.

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A 78-year-old patient has developed Haemophilus influenzae. In addition to standard precautions, what should the nurse use to protect herself and other patients when working within 3 feet of the patient?

  • A. Mask
  • B. Gown
  • C. Gloves
  • D. Shoe covers
Correct Answer: A

Rationale: Haemophilus influenzae is primarily transmitted via respiratory droplets. Wearing a mask is essential to prevent inhalation of these droplets within close proximity.

How many Toll-like receptors (TLRs) are found in humans?

  • A. 5
  • B. 8
  • C. 10
  • D. 12
Correct Answer: C

Rationale: The correct answer is C: 10. Toll-like receptors (TLRs) are a family of proteins involved in the innate immune response. In humans, there are 10 known TLRs that recognize different pathogen-associated molecular patterns. Each TLR is specific to different types of pathogens, allowing for a diverse recognition and response system. Therefore, the correct answer is 10. Choices A, B, and D are incorrect because they do not match the known number of TLRs in humans, which is 10.

Which of the following restriction endonucleases produce fragments with blunt ends?

  • A. Sacl
  • B. EcoRI
  • C. Smal
  • D. HindIII
Correct Answer: C

Rationale: The correct answer is C: Smal. Smal is a restriction endonuclease that cuts DNA at specific sequences, producing fragments with blunt ends. Smal recognizes the sequence CCCGGG and cuts between the two C's on both strands, resulting in blunt-ended fragments.

Explanation for incorrect choices:
A: Sacl - Sacl produces sticky ends, not blunt ends.
B: EcoRI - EcoRI produces sticky ends with overhangs.
D: HindIII - HindIII also produces sticky ends with overhangs.

In summary, Smal is the only enzyme among the choices that generates DNA fragments with blunt ends.

Which of the following statements is most correct? Immunoglobulin gene rearrangement:

  • A. Occurs after transcription of an immunoglobulin gene
  • B. Creates a complete V exon in the germline DNA
  • C. Creates a complete V exon in the B cell DNA
  • D. Both A and B are correct
Correct Answer: C

Rationale: The correct answer is C because immunoglobulin gene rearrangement creates a complete V exon in the B cell DNA. This process happens during B cell development, where segments of V, D, and J gene regions are rearranged to form a functional immunoglobulin gene. This rearrangement occurs before transcription, so option A is incorrect. Option B is incorrect because the V exon is not complete in the germline DNA, but rather created through rearrangement in the B cell DNA. Option D is incorrect as it combines two incorrect statements.

What is the primary effector cell in delayed-type hypersensitivity?

  • A. Mast cells
  • B. T cells
  • C. Neutrophils
  • D. B cells
Correct Answer: B

Rationale: The primary effector cell in delayed-type hypersensitivity is T cells. T cells play a crucial role in initiating and orchestrating the immune response in delayed hypersensitivity reactions. Upon exposure to the antigen, T cells are activated and release cytokines that recruit and activate macrophages, leading to the inflammatory response characteristic of delayed-type hypersensitivity. Mast cells are involved in immediate hypersensitivity reactions mediated by IgE. Neutrophils are primarily involved in acute inflammation and combating bacterial infections. B cells are responsible for antibody production in humoral immunity, not in delayed hypersensitivity reactions. Therefore, the correct answer is B: T cells.

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