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 researcher isolated a different single cell and determined that it was producing a certain protein. However, the protein was much shorter than it should have been. What kind of mutation likely occurred in this protein?