The question is incomplete. The complete question is as follows:
Which of the following mutations is most likely to cause a phenotypic change?
A) a duplication of all or most introns
B) a large inversion whose ends are each in intergenic regions
C) a nucleotide substitution in an exon coding for a transmembrane domain
D) a single nucleotide deletion in an exon coding for an active site
E) a frameshift mutation one codon away from the 3' end of the nontemplate strand
Answer: D) a single nucleotide deletion in an exon coding for an active site
Explanation:
Deletion or insertion of a single nucleotide in an axon coding for an active site is called frameshift mutation.
The sequence of codons is read during translation, in order to synthesize a amino acids chain and form a protein from the nucleotide sequence. Frameshift mutations occur when the usual codon sequence is broken by the deletion or addition of one or more nucleotides. For example, if only one nucleotide is removed from the axon sequence during the RNA splicing process, then there will be a disrupted reading frame for all codons before and after the mutation. This may result in several incorrect amino acids being introduced into the protein. Disruption in protein sequence will cause phenotypic change.
Hence, the correct option is D) a single nucleotide deletion in an exon coding for an active site
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