Final answer:
If G were added to the original DNA strand after the third base, the resulting mRNA would have a sequence of 5'-CAA CGT T GTG TCA CGC CC-3'. This addition would cause a frameshift mutation, resulting in a different amino acid sequence in the protein.
Step-by-step explanation:
If G were added to the original DNA strand after the third base, the resulting mRNA would look like 5'-CAA CGT T GTG TCA CGC CC-3'. The mRNA is synthesized by replacing T with U and keeping the same sequence as the added G.
This addition of G would cause a frameshift mutation, shifting the reading frame of the mRNA by one base. As a result, all codons downstream of the insertion would be read differently, leading to a completely different amino acid sequence in the protein. This change in the amino acid sequence can alter the structure, function, or stability of the protein.