Yes, HOMOZYGOTES is a Scrabble word!

Letter values in Scrabble US: H 4, O 1, M 3, O 1, Z 10, Y 4, G 2, O 1, T 1, E 1, S 1.

Is it a valid word?

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

(genetics) an organism having two identical alleles of a particular gene and so breeding true for the particular characteristic