Yes, TRANSPOSON is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, A 1, N 1, S 1, P 3, O 1, S 1, O 1, N 1.

Is it a valid word?

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

a segment of DNA that can become integrated at many different sites along a chromosome (especially a segment of bacterial DNA that can be translocated as a whole)

Also: jumping gene.