9. Mutations in the IL2RG gene cause approximately 30% of severe combined immuno

Question

9. Mutations in the IL2RG gene cause approximately 30% of severe combined immunodeficiency disorder cases (SCID). These mutations result in alterations to a protein component of cytokine receptors essential for proper development of the immune system. The IL2RG gene is composed of 8 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 the gene is 325 amino acids long). a. Nonsense mutation in coding region b. Insertion in Exon 1, causing frameshift c. Missense mutation d. Deletion of exon 2, in frame .

Explanation / Answer

a. nonsense mutations in coding region

nonsense mutations is coding regions except in exon 7 and exon 8 resulted in mormal amount and size of mRNA.

nonsense mmutations in exon 7 and exon 8 resulted in premature termination of mRNA.

b. insertion in exon I may have a little impact. it produces normal mRNA.

whereas frameshift mutations casuing deletions in exon 6 and exon7 would cause premature termination of mRNA.

c. missense mutations in exon 1 would result in normal amount and size of mRNA.

d. frame shift deletion early in exon2 would result in trace amounts of mRNA.

however, point mutations, insertions and deletions all over the exons would result in abnormal gamma chains of proteins.

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