A gene has acquired a mutation in which the protein product has an "extra" 50 amino acids at the end Which region of the gene was likely mutated? A) koding region
B) start codon
C) promoter sequence
D) terminator sequence
E) stop codon

E) stop codon

Explanation:  

There might occur many mutations during protein synthesis. One of these involves the stop codon. As the DNI that codifies for proteins divides into codons of three bases, insertions or deletions in these areas might alter the genes in a way that the message can not be readen in the correct form. The mutation in the reading frame is caused by the insertion or deletion of a certain number of nucleotides that are not multiple by three in an aminoacidic sequence. If a mutation alters the reading frame, an amino acid is placed incorrectly, and the DNI sequence will be readen differently. An alteration in the reading frame might cause a change in the stop codon in a new different position. In general, there occur deletions, which causes a shorter protein. But there are also insertions, which are responsible for the addition of genetic material, involving small or big new fragments.

i might be wrong but i think its a. let me know if i’m right and have a good rest of your day!