Please read the following scenario to answer the following question. 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, the researcher isolated and cultured a single cell from this group and 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

deletion or insertion of nucleotide from or in any coding sequence of the DNA

Explanation:

The mutation would be most harmful to the cells if it resulted in the deletion or insertion of nucleotide from or in any coding sequence of the DNA.

Deletion or insertion of a nucleotide from/into the coding sequence of DNA results in a frameshift mutation away from the original protein. Deletion/insertion of a nucleotide from/to the coding sequence of a DNA can cause a totally different protein to be synthesized from such DNA or, worse still, results in a nonfunctional protein. Both results could be grossly harmful to the cells.