Mutations that introduce stop codons cause a number of genetic diseases. For example, from 2% to 5% of the people who have cystic fibrosis possess a mutation that causes a premature stop codon in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). This premature stop codon produces a truncated form of CFTRthat is nonfunctional and results in the symptoms of cystic fibrosis . One possible way to treat people with genetic diseases caused by these types of mutations is to trick the ribosome into reading through the stop codon, inserting an amino acid in its place. Although the protein produced may have one altered amino acid, it is more likely to be at least partly functional than is the truncated protein produced when the ribosome stalls at the stop codon. Indeed, geneticists have conducted clinical trials of a drug called PTC124 on people with cystic fibrosis. This drug interferes with the ribosome’s ability to correctly read stop codons . On the basis of what you know about the mechanism of nonsense-mediated mRNA decay (NMD), would you expect NMD to pose a problem for this type of treatment? Why or why not?
Mutations that introduce stop codons cause a number of genetic diseases. For example, from 2% to 5% of the people who have cystic fibrosis possess a mutation that causes a premature stop codon in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). This premature stop codon produces a truncated form of CFTR
that is nonfunctional and results in the symptoms of cystic fibrosis . One possible way to treat people with genetic diseases caused by these types of mutations is to trick the ribosome into reading through the stop codon, inserting an amino acid in its place. Although the protein produced may have one altered amino acid, it is more likely to be at least partly functional than is the truncated protein produced when the ribosome stalls at the stop codon. Indeed, geneticists have conducted clinical trials of a drug called PTC124 on people with cystic fibrosis. This drug interferes with the ribosome’s ability to correctly read stop codons . On the basis of what you know about the mechanism of nonsense-mediated mRNA decay (NMD), would you expect NMD to pose a problem for this type of treatment? Why or why not?
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