1) Why do the two DNA strands need to be going in the opposite directions? (2-3 sentences) Hint: think about base pairing.

DNA strands run antiparallel to allow for proper base pairing. Adenine (A) must pair with thymine (T), and guanine (G) must pair with cytosine (C); this complementary pairing is only possible with antiparallel orientation due to the molecules' shapes and hydrogen bonding locations.