A slot-type gaming machine using an expandable symbol array to create a series of sequentially larger symbol arrays with the potential for additional or enhanced awards. The generation of the larger arrays can be performed through a variety a different mechanisms, such as the addition of a reel to the base array. The secondary arrays may be generated only under specific sets of circumstances that occur in the base array including, a winning pay line, the occurrence of a bonus triggering symbol, etc. To increase player interest in the game, some embodiments include allowing the player to determine where the additional symbols to create the larger array are placed in the base array.