A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed.
1 A statement that is completely unbiased is objective whereas a statement that is characterized by the thoughts and the views of the speaker is subjective.  Objective is not characterized by any previous experience of the speaker whereas subjective is certainly characterized by the previous experiences of the speaker.
science buzz. Switching between subjective and objective modes is the essence of the scientific modus operandi. Not many people seem to appreciate that. Science is all about riding two horses, maybe not in concert, but certainly alternately-and knowing when to switch from one to the other.