…

In every cell, the means of replication,
Monomers (they’re termed “nucleotides”)
A sugar and a base in combination
Link in helix, forming side by side;
Guanine will attach to cytosine
Always “G to C” or “C to G”
And thymine will as well, to adenine
With “T to A” or maybe “A to T”
The polymer called DNA is made
By adding monomers onto the end.
In living cells, a template strand will aid
The synthesis—the two strands now will bend
In double helix form, as we have seen.
The information carried in this strand
Will be transcribed by RNA; it’s been
Discovered that this process has a hand
In synthesizing proteins—but that’s still
To come—for now, we take a closer look
And see thymine replaced by uracil;
A slightly different way to write our book.

…
http://scienceblogs.com/pharyngula/2007/10/st_olaf_talk.php#more