Mutations in the IL2RG gene cause approximately 30 percent of severe combined immunodeficiency disorder (SCID) cases in humans. These mutations result in alterations to a protein component of cytokine receptors that are essential for proper development of the immune system. The IL2RG gene is composed of eight exons and contains upstream and downstream sequences that are necessary for proper transcription and translation. Below are some of the mutations observed. For each, explain its likely influence on the IL2RG gene product (assume its length to be 375 amino acids).
Missense mutation

검증된 단계별 안내

Step 1: Understand what a missense mutation is. A missense mutation is a single nucleotide change in the DNA sequence that results in the substitution of one amino acid for another in the protein product.

Step 2: Consider the effect of this amino acid substitution on the IL2RG protein. Since the protein is 375 amino acids long, a missense mutation changes only one amino acid, which may affect the protein's structure or function depending on the importance of that amino acid in the protein's active site or stability.

Step 3: Analyze whether the substituted amino acid has similar or different properties compared to the original. For example, a change from a hydrophobic to a hydrophilic amino acid could disrupt protein folding or receptor binding.

Step 4: Recognize that a missense mutation may lead to a partially functional protein, a nonfunctional protein, or sometimes no significant effect, depending on the location and nature of the amino acid change.

Step 5: Conclude that the likely influence of a missense mutation in the IL2RG gene is an altered protein product that may impair cytokine receptor function, potentially contributing to the SCID phenotype.

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주요 개념

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Missense Mutation

A missense mutation is a single nucleotide change that results in the substitution of one amino acid for another in the protein sequence. This can alter the protein's structure and function, potentially impairing its role, depending on the importance of the affected amino acid in the protein's active or binding sites.

IL2RG Gene and Protein Function

The IL2RG gene encodes the common gamma chain, a critical component of several cytokine receptors involved in immune cell development. Mutations in IL2RG can disrupt cytokine signaling, leading to severe combined immunodeficiency (SCID) by impairing the immune system's ability to develop and function properly.

Gene Structure and Expression

The IL2RG gene consists of eight exons and regulatory sequences upstream and downstream that control transcription and translation. Mutations affecting these regions or the coding exons can alter mRNA processing or protein synthesis, impacting the final protein product's length, structure, or abundance.

관련 실천

교과서 질문

Mutations in the IL2RG gene cause approximately 30 percent of severe combined immunodeficiency disorder (SCID) cases in humans. These mutations result in alterations to a protein component of cytokine receptors that are essential for proper development of the immune system. The IL2RG gene is composed of eight exons and contains upstream and downstream sequences that are necessary for proper transcription and translation. Below are some of the mutations observed. For each, explain its likely influence on the IL2RG gene product (assume its length to be 375 amino acids).

Large deletion covering Exons 2 and 3

594

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교과서 질문

Deletion in Exon 2, in frame

517

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교과서 질문

Insertion in Exon 1, causing frameshift

533

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교과서 질문