Consequently, there are four possible bases that could occur at each site along the DNA backbone and 4 × 4, or 42, or 16 possible two-base sequences (AA AT AG AC TA TG TC TT CG CT CC CA GA GG GC GT). Similarly, there are 4 × 4 × 4, or 43, or 64 possible three-base sequences. (I’ll refrain from listing them all.) That is, increasing the number of bases in a sequence from 1 to 2 to 3 increases the number of possibilities from 4 to 16 to 64. As the sequence length continues to grow, the number of combinatorial possibilities corresponding to sequences of increasing length inflates exponentially.
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