Which mutation is harmful to the organism?

Random mutations are very harmful

Explanation:

Spontaneous or random mutations are the most harmful mutations for any organism. It is due to the variance in the output of such mutations. Without any specific result generated due to such mutations, it become very difficult for a genetic engineer to treat these mutation and hence DNA replication is interrupted  in a random direction every time a molecule collides with in the moving cells.

b brown mice / white sand dunes