Final answer:
The insertion of two nucleotides into the middle of an mRNA molecule results in a frameshift mutation, altering the reading frame and the subsequent amino acid sequence, which often produces a non-functional protein and may introduce a premature stop codon.
Step-by-step explanation:
Effects of Inserting Two Nucleotides into mRNA
The insertion of two nucleotides into the middle of an mRNA molecule would cause a frameshift mutation. Since the genetic code is read in triplets of nucleotides, called codons, adding or subtracting nucleotides not in multiples of three can disrupt this reading frame. As a result, every codon downstream of the mutation would be altered, leading to a significant change in the amino acid sequence. This mutation can change the function of the protein, often rendering it non-functional. It could also introduce a premature stop codon, halting protein synthesis early.
Frameshift mutations are generally more severe the earlier they occur in the mRNA sequence because they affect a larger portion of the protein. While point mutations replace one nucleotide with another, frameshift mutations such as the insertion of two nucleotides do not fit this category. They are instead classified by their ability to shift the reading frame and inherently alter the protein's amino acid sequence dramatically.