While working with cultured mouse cells, a researcher unknowingly treated the cells with a mutagen that causes the deletion or insertion of individual nucleotides in DNA. Subsequently, she isolated and cultured a single cell from this group. She noticed that the progeny of this cell were not producing a certain protein and that this affected their survival.
The mutation would be most harmful to the cells if it resulted in .
A) substitution of a base pair
B) deletion of a triplet near the middle of the gene
C) a single nucleotide deletion near the end of the coding sequence
D) a single nucleotide in the middle of an intron
E) a single nucleotide insertion near the start of the coding sequence