Question

The deletion of a single base from a DNA molecule can be a fatal mutation. Substitution of one base for another is often not as serious a mutation. Why?

Short answer

Deletion will move the code reading frame, and all subsequent codes have mistakes because of the reading frame.

Step-by-step solution

The substitution of one base for another in DNA

Substitution is replacing one base with another one. In this situation, the mutation will not be harmful because only one amino acid might be replaced inside the code where the mutation occurs. Subsequent codes will stay the same.

Deletion of one base from a DNA

Deletion of the base can be more dangerous than substitution because deletion of one base can cause errors during meiosis. It removes code reading frames. After that, all subsequent codes are replaced with the new one because the reading frame is different.

Hence, deletion will move the code reading frame, and all subsequent codes have mistakes because of the reading frame.