Nokea
The class of immunoglobulins most abundant in body is:
- A. IgG
- B. IgE
- C. IgD
- D. IgM
Correct Answer: A
Rationale: The correct answer is A: IgG. IgG is the most abundant class of immunoglobulins in the body, constituting about 75% of total immunoglobulins. IgG plays a crucial role in long-term immunity, neutralizing toxins, and enhancing phagocytosis. IgE is involved in allergic reactions, IgD is mainly found on B cells and functions as a receptor, and IgM is the first antibody produced in response to an infection but is less abundant compared to IgG. Therefore, IgG is the correct choice based on its abundance and diverse functions in the immune system.
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Family Parvoviridae can cause all of these, except:
- A. Aplastic crisis in patients with chronic anemia
- B. Herpangina
- C. Fetal infections
- D. Fifth disease
Correct Answer: B
Rationale: The correct answer is B: Herpangina. Family Parvoviridae includes Parvovirus B19, which causes Fifth disease, aplastic crisis in chronic anemia, and fetal infections. Herpangina is caused by Enteroviruses, not Parvoviridae. Parvovirus B19 specifically targets erythroid progenitor cells, leading to anemia in susceptible individuals. Fetal infections can result in hydrops fetalis. Aplastic crisis occurs in patients with chronic anemia due to suppression of erythropoiesis by the virus.
Which of the following statements is FALSE regarding B cells?
- A. B cells that recognize high concentrations of antigen (self) in the absence of other signals undergo apoptosis in the bone marrow
- B. Bone marrow stem cells migrate to the thymus and develop into B cells
- C. B cells synthesize antibodies and put them on their cell surface
- D. B cells can undergo class switching and produce a different antibody type
Correct Answer: B
Rationale: B cells develop in the bone marrow, not the thymus. Firstly, hematopoietic stem cells in the bone marrow give rise to B cells. They undergo maturation and selection processes in the bone marrow, not in the thymus. Therefore, choice B is false. On the other hand, choices A, C, and D are correct. A is true because B cells with high affinity to self-antigens undergo apoptosis to prevent autoimmunity. C is true since B cells synthesize antibodies which can be displayed on their surface as B cell receptors. D is true because B cells can undergo class switching to produce different types of antibodies based on the immune response requirements.
Streptococci are:
- A. Gram-positive, short rod shaped bacteria and size 4-6 µm
- B. Gram-negative, rounded or lanceolate shape and size 0,5-1 µm
- C. Gram-negative, short rod shaped bacteria and size 4-6 µm
- D. Gram-positive, spherical or lanceolate shape and size 0,5-1 µm
Correct Answer: D
Rationale: The correct answer is D because Streptococci are Gram-positive bacteria, typically spherical in shape, and range from 0.5-1 µm in size.
A is incorrect as streptococci are not rod-shaped and are usually smaller in size. B is incorrect as they are not Gram-negative and are not typically of such small size.
C is incorrect as streptococci are not Gram-negative and are not usually rod-shaped. Thus, based on their characteristics, the correct answer is D.
Which is the most prominent immunoglobulin class present in external secretions
- A. IgG
- B. IgM
- C. IgA
- D. IgE
Correct Answer: C
Rationale: The correct answer is C: IgA. IgA is the most prominent immunoglobulin class present in external secretions like saliva, tears, and mucus. It plays a crucial role in mucosal immunity by preventing pathogens from entering the body. IgG is mainly found in the blood and tissues, IgM is the first antibody produced in response to an infection, and IgE is involved in allergic reactions. IgA's presence in external secretions helps protect the body from infections at mucosal surfaces, making it the correct choice in this context.
A specific sequence of three consecutive nucleotides that is part of the genetic code and that specifies a particular amino acid in a protein or starts or stops protein synthesis is called:
- A. Codon
- B. Primer
- C. Nucleosome
- D. Polypeptide
Correct Answer: A
Rationale: Step 1: Definition - A codon is a sequence of three nucleotides that code for a specific amino acid or signal the start/stop of protein synthesis.
Step 2: Function - Codons are essential for translating genetic information into proteins.
Step 3: Specificity - Codons are specific in their role of encoding amino acids.
Step 4: Examples - Examples like AUG for methionine and UAA, UAG, UGA for stop codons illustrate codon functionality.
Step 5: Summary - The correct answer is A (Codon) because it accurately describes the function and specificity of a three-nucleotide sequence in genetic coding. Choices B, C, and D are incorrect as they do not align with the definition and function of a codon.