Complementary strand for 5'–ACAGTAT–3' is 3'–TGTCATA–5'.
Nucleobase (guanine, cytosine, adeninem, thymine) on one strand bonds with just one type of nucleobase on the other strand (guanine-cytosine and adenine-thymine). Between adenine and thymine are two and between guanine and cytosine are three hydrogen bonds.
Hydrogen bonds: 5 × (adenine-thymine pair) + 2 × (guanine-cytosine pair) =
= 5 × 2 + 2 × 3 = 16.