Nokea
The human immunodeficiency virus (HIV)
- A. Is a retrovirus
- B. Is an RNA virus
- C. Is a lentivirus
- D. All of the above A, B and C
Correct Answer: D
Rationale: Step 1: HIV is a retrovirus because it contains RNA as its genetic material and uses the enzyme reverse transcriptase to convert its RNA into DNA.
Step 2: HIV is an RNA virus because its genetic material is RNA.
Step 3: HIV is a lentivirus which is a subgroup of retroviruses known for causing slow-progressing diseases.
Therefore, the correct answer is D as all statements A, B, and C are true based on the characteristics of HIV.
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Developing T cells in the thymus can express
- A. Both CD4 and CD8
- B. Only CD4
- C. Only CD8
- D. Neither CD4 or CD8
Correct Answer: A
Rationale: The correct answer is A because developing T cells initially express both CD4 and CD8 co-receptors in the thymus. This stage is crucial for T cell maturation and selection. Eventually, T cells undergo positive and negative selection processes to become either CD4+ helper T cells or CD8+ cytotoxic T cells based on their specificity and function. Choices B and C are incorrect because T cells initially express both CD4 and CD8. Choice D is also incorrect as T cells do express either CD4 or CD8 during their development in the thymus.
Elaborating on Jenner's observations, who is considered to have created the first "attenuated" vaccine
- A. Louis Pasteur
- B. Robert Koch
- C. Ilya Metchnikoff
- D. Adolf Von Behring
Correct Answer: A
Rationale: The correct answer is A: Louis Pasteur. He is considered to have created the first "attenuated" vaccine based on his work with the rabies vaccine in the 1880s. Pasteur's method involved weakening the virus to make it less harmful while still eliciting an immune response. Other choices are incorrect because:
B: Robert Koch is known for his contributions to microbiology and germ theory, not for creating the first attenuated vaccine.
C: Ilya Metchnikoff is known for his work on immunology and phagocytosis, not for developing the first attenuated vaccine.
D: Adolf Von Behring is known for his research on diphtheria antitoxin, not for creating the first attenuated vaccine.
VDJ gene rearrangement takes place in
- A. Germinal Centers
- B. Lymph Nodes
- C. Bone marrow
- D. Spleen
Correct Answer: C
Rationale: Rationale: VDJ gene rearrangement occurs during lymphocyte development to generate diverse antigen receptors. This process occurs in the bone marrow, specifically in the early stages of B cell development. In the bone marrow, B cell precursors undergo VDJ recombination to create unique antibody specificity. Germinal centers are sites for B cell activation and proliferation, not gene rearrangement. Lymph nodes and spleen are secondary lymphoid organs where mature lymphocytes are activated, not where VDJ recombination occurs.
The annotation C refers to which DNA component?
- A. Vector DNA
- B. Plasmid DNA
- C. Chromosomal DNA
- D. Recombinant DNA
Correct Answer: C
Rationale: The correct answer is C: Chromosomal DNA. Chromosomal DNA refers to the DNA found in the chromosomes of an organism's nucleus, carrying the majority of its genetic information. In molecular biology, the annotation C typically refers to the chromosomal DNA of the organism being studied. Plasmid DNA (choice B) and vector DNA (choice A) are extrachromosomal DNA elements that are separate from the chromosomal DNA. Recombinant DNA (choice D) is a DNA molecule formed by combining DNA from different sources, which can include chromosomal, plasmid, or vector DNA. Therefore, the correct choice is C as it specifically refers to the chromosomal DNA component.
The class of an immunoglobulin
- A. is determined by Class I and Class II major histocompatibility complex proteins
- B. is determined by the carbohydrate attached to the light chain is
- C. determined by the antigen
- D. is determined by the heavy chain type
Correct Answer: D
Rationale: The correct answer is D because the class of an immunoglobulin is determined by the type of heavy chain it possesses. There are five main classes of immunoglobulins (IgG, IgA, IgM, IgD, IgE) which are defined by the heavy chain constant region. Different heavy chain types result in different effector functions and biological properties. Choices A, B, and C are incorrect because the class of an immunoglobulin is not determined by Class I and Class II major histocompatibility complex proteins, carbohydrate attached to the light chain, or the antigen. These factors may influence the function or specificity of the antibody, but they do not determine its class.