The original DNA strand

The four bases are tightly linked along the length of the strand.

The strand is coiled tightly into a double helix.

The section ACG is the genetic code word for the amino acid Threonine.

It is not Threonine itself but only a chemical sequence that will recognize a certain amino acid.

When replication occurs

The old "zipper" starts to open at one end.

The new "zipper" starts to close at the loose ends by attaching free floating bases.

Wow!

Two new exact copies of the original molecule

Note that the code word in the original strand has been copied faithfully into the new strands.