Paper and pencils, codon tables, Biology Workbench.
This activity is a derivative of the old telephone game. Instead of using a secret you use a string of letters that the person must write down (transcribe) onto a piece of paper. Then they read their string to another person who now becomes the scribe and writes down (replicates) what they can onto a piece of paper and so on until everyone in the room has written down (replicated) the secret code that they received from one other person.
The secret code is a series of As, Cs, Gs, and Ts. You can reverse engineer the nucleic acid code to spell out a word in the single letter amino acid code. Just be aware that not all letters are represented:
avoid B, J, O, U, X and Z.
Next you supply them with a codon chart that uses the single-letter amino acid codes and everybody translates their message into an amino acid sequence.
After everyone translates their message, write down the results on the board in the same order that the messages were received. Students are amazed at how quickly the sequence "mutates" (or evolves) in a short time.
Then the really nice part of it is that the class has generated data that can be used to explore some of the programs in Biology Workbench, such as CLUSTALW. Students can input both the DNA and protein sequence data and see if it changes the relationship of the sequences to each other.
Although I haven't done it, I would like to experiment with changing the gap penalty associated with CLUSTALW.