The Type of Mutation Causing I-Cell Disease

What type of mutation causes many cases of I-cell disease and where is it located?

The type of mutation that causes many cases of I-cell disease is a missense mutation. The mutation occurs at the third codon, where the amino acid changes from Phenylalanine (Phe) to Leucine (Leu).

Understanding the Mutation Leading to I-Cell Disease

Mutation Type: The mutation responsible for many cases of I-cell disease is a missense mutation. This type of mutation involves a single nucleotide change that results in the substitution of one amino acid for another in the protein chain.

Location of the Mutation:

Amino Acid Position: The mutation occurs at the third codon, specifically at amino acids 372-376 within the gene sequence.

Determining the Mutation:

In order to determine the type of mutation causing I-cell disease, we transcribe and translate both the wildtype and mutant gene sequences. By comparing the resulting amino acid sequences, we can pinpoint where the mutation occurs and what specific amino acid change is responsible for the disease.

Let's walk through the process for both the wildtype and mutant gene sequences:

Wild Type Gene Sequence:

Template Strand: 3’ CTA CAA AAA GCT TTA 5’
5’ GAT GTT TTT CGA AAT 3’

mRNA: 5’ GAU GUU UUU CGA AAU 3’

Amino Acids: Aspartic Acid (Asp) - Valine (Val) - Phenylalanine (Phe) - Arginine (Arg) - Asparagine (Asn) at position 372-376.

Mutant Gene Sequence:

Template Strand: 3’ CTA CAA GAA GCT TTA 5’
5’ GAT GTT CTT CGA AAT 3’

mRNA: 5’ GAU GUU CTT CGA AAU 3’

Amino Acids: Aspartic Acid (Asp) - Valine (Val) - Leucine (Leu) - Arginine (Arg) - Asparagine (Asn) at position 372-376.

By comparing the amino acid sequences of the wildtype and mutant genes, we identified the missense mutation at the third codon, resulting in the substitution of Phenylalanine (Phe) with Leucine (Leu). This mutation is the cause of I-cell disease in many cases.