Infantile cardiomyopathy is a devastating disorder that is fatal during the first year of life due to defects in the function of heart muscles resulting from mitochondrial dysfunction. A study, performed by Götz et al. [(2011). Am. J. Hum. Genet. 88:635–642), identified two different causative mutations in the gene for mitochondrial alanyl-tRNA synthetase (mtAlaRS). One mutation changes a leucine residue at amino acid position 155 to arginine (p.Leu155Arg). The other mutation changes arginine at position 592 to tryptophan (p.Arg592Trp). The mtAlaRS enzyme has an N-terminal domain (amino acids 36–481) that catalyzes tRNA aminoacylation and an internal editing domain (amino acids 484–782) that catalyzes deacylation in the case that the tRNA is charged with the wrong amino acid.
Which mutation would you predict has a more severe impairment of translation in mitochondria, and why?
17. Mutation, Repair, and Recombination
Types of Mutations
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Which of the following mutations changes one codon to a chemically different amino acid?
A
Silent mutation
B
Conservative missense mutation
C
Nonconservative missense mutation
D
Nonsense mutations
Verified step by step guidance1
Understand the types of mutations: Silent mutations do not change the amino acid sequence, conservative missense mutations change the amino acid to one with similar properties, nonconservative missense mutations change the amino acid to one with different properties, and nonsense mutations introduce a stop codon.
Identify the mutation type that changes the codon to a chemically different amino acid: A nonconservative missense mutation alters the amino acid to one with different chemical properties.
Consider the impact of a nonconservative missense mutation: This type of mutation can affect protein function due to the change in chemical properties of the amino acid.
Compare the mutation types: Silent mutations do not affect the protein's function, conservative missense mutations have minimal impact, and nonsense mutations can truncate the protein.
Conclude that a nonconservative missense mutation is the correct answer as it changes the codon to a chemically different amino acid, potentially altering protein function significantly.
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