Final answer:
The most likely mutation to cause a phenotypic change is a single nucleotide deletion in an exon coding for an active site. This type of mutation leads to a frameshift mutation which can severely affect the protein's structure and functionality, resulting in significant phenotypic changes.
So, the correct answer is E.
Step-by-step explanation:
The mutation most likely to cause a phenotypic change is E. a single nucleotide deletion in an exon coding for an active site. This is because active sites are crucial for the functionality of proteins, often being the region where substrate binding and catalysis occur. A single nucleotide deletion here can cause a frameshift mutation, which changes the reading frame of the protein coding sequence, leading to an entirely different set of amino acids being incorporated downstream from the mutation site. These changes can drastically alter the protein's structure and function, potentially leading to significant phenotypic effects.
While all mutations can potentially lead to changes in phenotype, most others, such as the ones presented in the options A, B, C, and D, are either not located in critical regions, like the active site, or the frameshift is too close to the end of the gene to cause a significant change. Inversions and duplication of introns, in general, do not affect the protein-coding sequence, whereas a substitution in a transmembrane domain may or may not change the protein function significantly, depending on whether the substitution is conservative or not.
An important note regarding frameshift mutations is that if they occur close to the 3' end of the gene, the impact might be minimized because most of the protein would be translated correctly before the mutation site.
So, the correct answer is E. a single nucleotide deletion in an exon coding for an active site