Yes, MUTATION is a Scrabble word!

Letter values in Scrabble US: M 3, U 1, T 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

MUTATION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(biology) an organism that has characteristics resulting from chromosomal alteration
(genetics) any event that changes genetic structure; any alteration in the inherited nucleic acid sequence of the genotype of an organism
a change or alteration in form or qualities

Also: genetic mutation, chromosomal mutation.