Deterministic polynomial-time algorithms for designing short DNA words

Designing short DNA words is a problem of constructing n DNA strings (words) with the minimum length such that the Hamming distance between each pair is at least k and the words satisfy a set of extra constraints. This problem has applications in DNA computing, DNA self-assembly, and DNA arrays. Previous works include those that extended results from coding theory to obtain bounds on code size for biologically motivated constraints and those that applied heuristic local searches, genetic algorithms, and randomized algorithms. In particular, Kao, Sanghi and Schweller developed polynomial-time randomized algorithms to construct n DNA words of length 9· max {logn,k} satisfying a sets of constraints with high probability. In this paper, we give deterministic polynomial-time algorithms to construct DNA words based on expander codes, Ramanujan graphs, and derandomization techniques. Our algorithms can construct n DNA words of length max {3logn, 4k} or 2.1 logn + 6.28 k satisfying the same sets of constraints as the words constructed by the algorithms of Kao et al. We have also extended these algorithms to construct words that satisfy a larger set of constraints for which the algorithms of Kao et al. do not work.