AACGTGC There are four bases in DNA. A(adenine), C(cytosine), G(guanine), and T(thymine). For each base, there's one complement. C will only bond with G and A will only bond with T. So let's write down the sequence with each base on it's own line and then the complementary base afterwards. T <-> A T <-> A G <-> C C <-> G A <-> T C <-> G G <-> C So the complementary base sequence to TTGCACG is AACGTGC.