Immunogenetics Questions: Test! Quiz
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- 1.
The greater hypervariability of the CDR3 region compared to the CDR1 region of immunoglobulin heavy chains can be partly attributed to the enzyme terminal deoxyribonucleotide transferase because of its role in:
- A.
Precise nucleotide splicing during gene rearrangement
- B.
Somatic hypermutation
- C.
Switch recombination.
- D.
Combinatorial diversity
- E.
Non template nucleotide additions
Correct Answer
E. Non template nucleotide additionsExplanation
The greater hypervariability of the CDR3 region compared to the CDR1 region of immunoglobulin heavy chains can be partly attributed to the enzyme terminal deoxyribonucleotide transferase because it is responsible for adding non-template nucleotides during V(D)J recombination. This process allows for the generation of a diverse repertoire of antibodies by introducing random nucleotide sequences into the CDR3 region, increasing its variability. This variability is essential for the immune system to recognize and bind to a wide range of antigens.Rate this question:
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- 2.
When a B-cell undergoes immunoglobulin class switching:
- A.
The variable region of the light chain changes, but its constant region remains the same
- B.
The variable region of the light chain remains the same, but its constant region changes.
- C.
The variable region of the heavy chain remains the same but its constant region changes
- D.
The variable region of the heavy chain changes but its constant region remains the same
- E.
Both the variable and constant regions change
Correct Answer
C. The variable region of the heavy chain remains the same but its constant region changesExplanation
When a B-cell undergoes immunoglobulin class switching, the variable region of the heavy chain remains the same but its constant region changes. This process allows the B-cell to produce antibodies with different effector functions while maintaining the same antigen specificity. The variable region is responsible for binding to the antigen, while the constant region determines the antibody's effector functions, such as activating complement or binding to Fc receptors. Therefore, by changing the constant region, the B-cell can switch from producing one class of antibody (e.g., IgM) to another (e.g., IgG or IgA) without altering its antigen specificity.Rate this question:
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- 3.
As predicted by the clonal selection hypothesis, B cells express cell-surface IgM of the same specificity as the IgM produced for secretion. This is possible because of:
- A.
Switch recombination
- B.
Productive V(D)J recombination on both alleles
- C.
Selective pressure
- D.
Alternative polyA site usage
- E.
Post-translational modifications of the primary protein product
Correct Answer
D. Alternative polyA site usageExplanation
Alternative polyA site usage refers to the phenomenon where different polyadenylation sites within a gene are used, resulting in the production of alternative mRNA transcripts with different 3' untranslated regions (UTRs). In the context of B cells, alternative polyA site usage allows for the expression of cell-surface IgM of the same specificity as the IgM produced for secretion. This is because the alternative polyA sites regulate the length of the 3' UTR, which in turn affects the stability and translation efficiency of the mRNA. Thus, alternative polyA site usage ensures that B cells can produce both cell-surface and secreted IgM molecules with the same specificity.Rate this question:
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- 4.
Which of the following does not contribute to the generation of diversity of B-cell antigen receptors?
- A.
Multiple V genes in the germ line
- B.
Random assortment of L and H chains
- C.
Imprecise recombination of V and J or V, D, and J segments
- D.
Inheritance of multiple C-region genes
- E.
Somatic mutation
Correct Answer
D. Inheritance of multiple C-region genesExplanation
Inheritance of multiple C-region genes does not contribute to the generation of diversity of B-cell antigen receptors. The diversity of B-cell antigen receptors is primarily generated through the rearrangement and recombination of V, D, and J segments, as well as the random assortment of L and H chains. These processes allow for the creation of a wide variety of antigen receptor sequences. The inheritance of multiple C-region genes, on the other hand, affects the constant region of the antibody molecule and does not contribute to the generation of diversity in the variable region, where antigen binding occurs.Rate this question:
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- 5.
After binding to its specific antigen, a B lymphocyte may switch its:
- A.
Immunoglobulin light-chain isotype
- B.
Immunoglobulin heavy-chain class
- C.
The variable region of the immunoglobulin heavy chain
- D.
The constant region of the immunoglobulin light chain
Correct Answer
B. Immunoglobulin heavy-chain classExplanation
B lymphocytes have the ability to switch their immunoglobulin heavy-chain class after binding to their specific antigen. This process is known as class switching and it allows B cells to produce different classes of antibodies (IgM, IgG, IgA, IgE) with the same antigen specificity. This class switching occurs through a process called somatic recombination, where DNA rearrangements take place in the immunoglobulin heavy-chain gene locus. This allows B cells to adapt their immune response to different types of pathogens and enhances the effectiveness of the immune system.Rate this question:
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- 6.
“Isotype switching” of immunoglobulin classes by B cells involves:
- A.
Simultaneous insertion of VH genes adjacent to each CH gene
- B.
Successive insertion of a single VH gene adjacent to different CH genes
- C.
Activation of homologous genes on chromosome 6
- D.
Switching of light-chain types (kappa and lambda)
Correct Answer
B. Successive insertion of a single VH gene adjacent to different CH genesExplanation
Isotype switching of immunoglobulin classes by B cells involves the successive insertion of a single VH gene adjacent to different CH genes. This process allows B cells to change the class of immunoglobulin they produce without altering the specificity of the antibody. By switching the constant region of the antibody, B cells can produce different types of immunoglobulins with distinct effector functions, such as IgM, IgG, IgA, and IgE. This process is important for the immune system to mount appropriate responses against different types of pathogens and antigens.Rate this question:
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- 7.
During the maturation of a B lymphocyte, the first immunoglobulin heavy chain synthesized is the:
- A.
Mu chain
- B.
Gamma chain
- C.
Epsilon chain
- D.
Alpha chain
Correct Answer
A. Mu chainExplanation
During the maturation of a B lymphocyte, the first immunoglobulin heavy chain synthesized is the Mu chain. This is because the Mu chain, also known as the IgM heavy chain, is the first heavy chain produced during B cell development. It is expressed on the surface of immature B cells and is associated with the IgM antibody. As B cells continue to mature, they can switch to producing other heavy chains, such as gamma, epsilon, or alpha chains, which are associated with different types of immunoglobulins. However, the Mu chain is the initial heavy chain synthesized during B cell maturation.Rate this question:
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- 8.
The antibody-binding site is formed primarily by:
- A.
The constant regions of H and L chains
- B.
The hypervariable regions of H and L chains
- C.
The hypervariable regions of H chains
- D.
The variable region of H chains
- E.
The variable region of L chains
Correct Answer
B. The hypervariable regions of H and L chainsExplanation
The hypervariable regions of H and L chains form the antibody-binding site. These regions contain amino acid sequences that are highly variable and are responsible for recognizing and binding to specific antigens. The constant regions of H and L chains, on the other hand, are involved in other functions such as antibody structure and signaling. Therefore, the correct answer is the hypervariable regions of H and L chains.Rate this question:
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- 9.
An individual who is heterozygous for Gm allotypes contains two allelic forms of IgG in serum, but individual lymphocytes produce only one of the two forms. This phenomenon, known as “allelic exclusion,” is consistent with
- A.
A rearrangement of a heavy-chain gene on only one chromosome in a lymphocyte
- B.
Rearrangements of heavy-chain genes on both chromosomes in a lymphocyte
- C.
A rearrangement of a light-chain gene on only one chromosome in a lymphocyte
- D.
Rearrangements of light-chain genes on both chromosomes in a lymphocyte
Correct Answer
A. A rearrangement of a heavy-chain gene on only one chromosome in a lymphocyteExplanation
The correct answer is "A rearrangement of a heavy-chain gene on only one chromosome in a lymphocyte." This is because allelic exclusion refers to the phenomenon where only one allele is expressed in a cell, while the other allele is silenced. In the case of Gm allotypes, which are variations in the constant region of IgG antibodies, the individual has two allelic forms of IgG in their serum. However, in individual lymphocytes, only one form is produced. This suggests that there is a rearrangement of the heavy-chain gene on only one chromosome in the lymphocyte, leading to the expression of only one form of IgG.Rate this question:
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- 10.
The hypervariable region of an antibody light chain results from: (concept – how antibody hypervariable regions are generated)
- A.
Alternative splicing of the corresponding pre-RNA during maturation.
- B.
Clipping the amino-terminal end of the polypeptide during secretion
- C.
Presence of multiple J segments within the corresponding gene.
- D.
Presence of multiple LV segments within the corresponding gene
- E.
Addition of nucleotides between LV and J segments in maturing lymphocytes
Correct Answer
E. Addition of nucleotides between LV and J segments in maturing lymphocytesExplanation
During the maturation of lymphocytes, the hypervariable region of an antibody light chain is generated through the addition of nucleotides between LV and J segments. This process, known as V(D)J recombination, involves the rearrangement of gene segments to generate a diverse repertoire of antibodies. The addition of nucleotides between LV and J segments introduces random variations in the DNA sequence, leading to the production of antibodies with different antigen-binding specificities. This mechanism allows the immune system to recognize and respond to a wide range of pathogens.Rate this question:
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- 11.
Cells express cell-surface IgM of the same specificity as the IgM produced for secretion. This is possible because of: (concept – how soluble IgM is generated)
- A.
Switch recombination
- B.
Productive V(D)J recombination on both alleles
- C.
Selective pressure
- D.
Alternative splicing of a primary RNA transcript.
- E.
Post-translational modifications of the primary protein product
Correct Answer
D. Alternative splicing of a primary RNA transcript.Explanation
The correct answer is alternative splicing of a primary RNA transcript. Alternative splicing is a process in which different exons of a primary RNA transcript are combined in different ways to generate multiple mRNA isoforms. In the case of cells expressing cell-surface IgM, alternative splicing allows for the generation of membrane-bound IgM molecules that have the same specificity as the IgM produced for secretion. This process ensures that the cells can display the same IgM on their surface as they secrete, allowing for efficient immune responses.Rate this question:
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- 12.
An IgG2 molecule is composed of which of the following?
- A.
One alpha, one gamma2, and two kappa chains
- B.
One gamma1 chain and two kappa chains
- C.
Two gamma1 chains and one kappa and one lambda chain
- D.
Two gamma1 chains and two kappa chains
- E.
Two gamma2 chains and two kappa chains
Correct Answer
E. Two gamma2 chains and two kappa chainsExplanation
An IgG2 molecule is composed of two gamma2 chains and two kappa chains. This is because immunoglobulin G (IgG) molecules are made up of two heavy chains and two light chains. In the case of IgG2, the heavy chains are gamma2 chains and the light chains are kappa chains. Therefore, the correct answer is two gamma2 chains and two kappa chains.Rate this question:
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- 13.
The earliest stages of B-cell differentiation:
- A.
Occur in the embryonic thymus
- B.
Require the presence of antigen
- C.
Involve rearrangement of -chain gene segments
- D.
Involve the rearrangement of surrogate light-chain gene segments
- E.
Involve a rearrangement of heavy-chain gene segments
Correct Answer
E. Involve a rearrangement of heavy-chain gene segmentsExplanation
The correct answer is that the earliest stages of B-cell differentiation involve a rearrangement of heavy-chain gene segments. This is because during B-cell development, the genes that encode the heavy chains of antibodies undergo a process called V(D)J recombination. This process involves the rearrangement and joining of different gene segments, including V (variable), D (diversity), and J (joining) segments, to generate a diverse repertoire of heavy-chain genes. This rearrangement is crucial for the production of functional antibodies with a wide range of antigen specificities.Rate this question:
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Current Version
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Mar 21, 2023Quiz Edited by
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Jun 08, 2012Quiz Created by
Rosssweetie
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