Refer to the table. Alkaptonuria is an inborn error of metabolism, caused by defects in an enzyme in the pathway that breaks down tyrosine (see Section 14.1).Humans who are homozygous for one of these mutations make nonfunctional enzyme and accumulate the enzyme's substrate, homogentisic acid, which causes their disease symptoms.In 1996, researchers in Spain cloned and sequenced the gene for the enzyme and characterized several mutant alleles.The table shows the wild-type coding strand sequence for part of the gene and the corresponding region from one of the mutant alleles.What type of mutation is this?
A) Silent
B) Nonsense
C) Frame-shift
D) Missense
E) Reversion

Question

Refer to the table.  Alkaptonuria is an inborn error of metabolism, caused by defects in an enzyme in the pathway that breaks down tyrosine (see Section 14.1).Humans who are homozygous for one of these mutations make nonfunctional enzyme and accumulate the enzyme's substrate, homogentisic acid, which causes their disease symptoms.In 1996, researchers in Spain cloned and sequenced the gene for the enzyme and characterized several mutant alleles.The table shows the wild-type coding strand sequence for part of the gene and the corresponding region from one of the mutant alleles.What type of mutation is this?
A) Silent 
B) Nonsense 
C) Frame-shift 
D) Missense 
E) Reversion

Quizplus · Accepted Answer

The mutation shown in the table is a missense mutation, which results in a change in a single nucleotide that leads to a change in the corresponding amino acid in the protein sequence. Specifically, the third codon in the wild-type sequence (GCT) is changed to a different codon (ACT) in the mutant sequence, resulting in a different amino acid (threonine instead of alanine) at that position in the protein.

Refer to the Table