Before Beta 5, players received 200 turns per hour with 5000 turns maximum, while players who had donated in the previous 90 days could receive 350 turns with 10,000 max.
Now, however, non-donators receive 500 turns per hour and 10,000 maximum. Donators get 650 per hour with a cap of 20,000. Turns are gained at the fourth minute of every hours.
These turns may be used replicate DNA, clone DNA, perform an action with an army (attack, destroy, scout, steal, move), or harvest crop.
If on a shortage of turns, more can be purchased through the use of GC by going to Ledger -> GC Items. Because turns are such a crucial component of the game, the use of donation to gain an unfair advantage has been greatly criticized by all types of players.