  We report spin-selective tunneling of electrons along natural and artificial
double-stranded DNA (dsDNA) sandwiched by nonmagnetic leads. The results reveal
that the spin polarization strongly depends on the dsDNA sequence and is
dominated by its end segment. Both genomic and artificial dsDNA could be
efficient spin filters. The spin-filtering effects are sensitive to point
mutation which occurs in the end segment. These results are in good agreement
with recent experiments and are robust against various types of disorder, and
could help for designing DNA-based spintronic devices.
