Final answer:
A point mutation in a regulatory region of a gene is least likely to result in amino acid substitution in the protein product.
Step-by-step explanation:
The correct answer is C. Amino acid substitution in the protein product.
A point mutation in a regulatory region of a gene refers to a change in a single nucleotide in the DNA sequence. This type of mutation primarily affects gene expression and regulation. The regulatory region of a gene includes the promoter and enhancer regions, which play a crucial role in controlling gene transcription.
A point mutation in the regulatory region can alter the binding of transcription factors to the DNA sequence, affecting the rate of transcription and ultimately gene expression. It may also impact promoter efficiency, affecting the initiation and efficiency of transcription. Changes in mRNA stability can occur due to mutations in the 5'UTR or binding sites for RNA binding proteins.
However, amino acid substitution in the protein product is the least likely change to arise from a point mutation in a regulatory region. Point mutations in the regulatory region primarily affect gene expression and regulation, not the amino acid sequence of the resulting protein.