Yes, DOMINANTS is a Scrabble word!

Letter values in Scrabble US: D 2, O 1, M 3, I 1, N 1, A 1, N 1, T 1, S 1.

Is it a valid word?

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

(music) the fifth note of the diatonic scale
an allele that produces the same phenotype whether its paired allele is identical or different

Also: dominant allele.