Ligase Chain Rxn Fatal familial insomnia is an autosomal dominant disease caused
ID: 261003 • Letter: L
Question
Ligase Chain Rxn Fatal familial insomnia is an autosomal dominant disease caused by a point mutation in codon 178 of the prion protein gene PRNP. This point mutation changes a G into an A resulting in an amino acid change from aspartic acid to asparagine. People suffering from this disease suffer from insomnia that will eventually lead to hallucinations, delirium and death. This protein is expressed in a number of tissues but is predominantly expressed in neurons. The normal protein is found attached to synaptic membranes where it is thought to play a role in copper transport. The mutant protein forms aggregates inside the neuron. Several patients suffering from insomnia came in to be tested for this disease. Brently performed ligase chain reaction using primers that detect the correct "G" nucleotide and got the following results: P1 P2 P3 a. (2 pts) Tell me what the results show for patient 1 in terms of which nucleotide they have. b. (2 pts) Tell me what the results show for patient 2 in terms of which nucleotide they have. c. (2 pts)_Tell me what the results show for patient 3 in terms of which nucleotide they have d. (2 pts) _Which patient has fatal familial insomnia? e. (2 pts) Propose a mechanism by which this mutant protein might cause disruption in neuron function.Explanation / Answer
Please find the answers below:
Answer a: According to the information, ligase chain reaction has been conducted for detection of the nucleotide, hence, presence of an amplicon on the gel always represents the presence of a nucleotide. The lower band width for patient 1 demonstrates that it is heterozygous for this gene.
Answer b: Since the band width for patient 2 is large, this means that the patient contains more than one copy of the allele and hence is homozygous for the disease.
Answer c: The absence of band in this patient represents altogether absence of binding of the ligase to a nucleotide from the sample, thus suggesting normal healthy individual.
Answer d: According to the information, the disease is inherited in autosomal dominant manner, so both homozygous and heterozygous individuals will be affected from the disease. This gives that patient 1 and 2 both suffer from this disease.
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