Yes, DISSECTING is a Scrabble word!

Letter values in Scrabble US: D 2, I 1, S 1, S 1, E 1, C 3, T 1, I 1, N 1, G 2.

Is it a valid word?

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

cut open or cut apart
make a mathematical, chemical, or grammatical analysis of; break down into components or essential features

Also: break down, take apart.