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, 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

Answer 1

Answer: Option B) deletion of a triplet near the middle of the gene

Explanation:

The mutagen attack must have caused frameshift mutation, a type of mutation where the sequence of DNA is misread.

Furthermore, deletion, which involves the removal of a base or a triplet code is usually harmful because it is irreversible. Hence, the inability of cells to produce certain protein meant for their survival.

Thus, the most harmful effect is the deletion of a triplet near the middle of the gene