Final answer:
The deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein could explain the results.
Step-by-step explanation:
The question pertains to mutations in gene X and their potential effects on the resulting protein's structure and function. Mutations such as the introduction of a stop codon early in the gene (nonsense mutation), altering the start codon, modifying the ubiquitination sites, or affecting splicing, can all have profound impacts on protein functionality.
Option (a) introduces a stop codon at the fourth amino acid, which is an example of a nonsense mutation. This would result in a truncated protein, likely non-functional due to its significantly reduced size. Option (b) changes the start codon ATG to CCA, which would likely impair the initiation of translation and prevent the production of protein X. Option (c) removes sites for ubiquitin attachment, potentially altering the protein's stability and degradation. Lastly, option (d) involves a change at a splice site preventing proper RNA splicing, possibly leading to a non-functional protein due to the inclusion of incorrect exons or the exclusion of necessary ones.
Understanding the effect of each mutation type is essential. A frameshift mutation can occur through insertions or deletions of nucleotides, disrupting the entire downstream amino acid sequence. A substitution mutation can be missense, resulting in a different amino acid, or nonsense, introducing a premature stop codon. Either way, these mutations can drastically change the protein's structure and function, leading to non-functional proteins or potentially giving rise to new traits.