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The phenomenon of expression of only one allele of an immunoglobulin gene in lymphocytes is known as
- a)allelic exclusion
- b)allelic inclusion
- c)allelic variation
- d)allelic heterogeneity
Correct answer is option 'A'. Can you explain this answer?
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The phenomenon of expression of only one allele of an immunoglobulin g...
Allelic exclusion is a process that occurs in antibody producing lymphocytes (B-cells) where antibody synthesis is specified by only one in the pair of alleles of the relevant gene.
This is because only one of the alleles is allowed to be active.
Therefore, correct option is (a)
Note : B-cells are diploid. So they will have 2 alleles for a given antibody gene. But only one of them is expressed. This is called allelic exclusion.
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The phenomenon of expression of only one allele of an immunoglobulin g...
Allelic Exclusion in Lymphocytes
Definition: Allelic exclusion is the phenomenon of expressing only one allele of a gene in a cell, while the other allele is silenced or inactivated during the development of lymphocytes.
Explanation: In B cells, immunoglobulin genes are composed of multiple gene segments, including V (variable), D (diversity), and J (joining) segments. During B cell development, the genes undergo a process called V(D)J recombination, which randomly combines one V, one D, and one J segment to form a unique immunoglobulin gene. This process generates a vast repertoire of immunoglobulin genes, which can recognize a wide range of antigens.
However, expression of both alleles of an immunoglobulin gene in a single B cell can lead to the production of two different immunoglobulin molecules, which can recognize different antigens. This can result in self-reactive B cells, which can trigger autoimmune diseases.
To prevent this, the B cells undergo allelic exclusion, which ensures that only one of the two alleles of an immunoglobulin gene is expressed in a B cell. This is achieved by a feedback mechanism, where the expression of one allele inhibits the expression of the other allele. This mechanism is also regulated by epigenetic modifications, such as DNA methylation and histone acetylation, which affect the accessibility of the immunoglobulin genes to the transcription machinery.
Importance: Allelic exclusion is crucial for the generation of a diverse but self-tolerant immune system. It ensures that each B cell expresses a single, functional immunoglobulin molecule that can specifically recognize one antigen. This allows the immune system to respond to a wide range of pathogens while avoiding self-reactivity.
Definition: Allelic exclusion is the phenomenon of expressing only one allele of a gene in a cell, while the other allele is silenced or inactivated during the development of lymphocytes.
Explanation: In B cells, immunoglobulin genes are composed of multiple gene segments, including V (variable), D (diversity), and J (joining) segments. During B cell development, the genes undergo a process called V(D)J recombination, which randomly combines one V, one D, and one J segment to form a unique immunoglobulin gene. This process generates a vast repertoire of immunoglobulin genes, which can recognize a wide range of antigens.
However, expression of both alleles of an immunoglobulin gene in a single B cell can lead to the production of two different immunoglobulin molecules, which can recognize different antigens. This can result in self-reactive B cells, which can trigger autoimmune diseases.
To prevent this, the B cells undergo allelic exclusion, which ensures that only one of the two alleles of an immunoglobulin gene is expressed in a B cell. This is achieved by a feedback mechanism, where the expression of one allele inhibits the expression of the other allele. This mechanism is also regulated by epigenetic modifications, such as DNA methylation and histone acetylation, which affect the accessibility of the immunoglobulin genes to the transcription machinery.
Importance: Allelic exclusion is crucial for the generation of a diverse but self-tolerant immune system. It ensures that each B cell expresses a single, functional immunoglobulin molecule that can specifically recognize one antigen. This allows the immune system to respond to a wide range of pathogens while avoiding self-reactivity.
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The phenomenon of expression of only one allele of an immunoglobulin gene in lymphocytes is known asa)allelic exclusion b)allelic inclusion c)allelic variation d)allelic heterogeneityCorrect answer is option 'A'. Can you explain this answer?
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