A property of double-stranded DNA whereby one strand has the same base sequence (5'-to-3') as its complementary strand (5'-to-3'), which allows it to bind to a homodimeric or homotetrameric binding protein, e.g. the lac repressor. In practice, the term is applied to polynucleotide sequences that are more extensive, but have less perfect symmetry, than the palindromic sequences that are sites of restriction nuclease cleavage.