A deadly strain of bacteria has been accidentally introduced on Earth by a spaceship returning from Mars. The bacteria produce a toxin that is highly poisonous and a vaccine to protect society is drastically needed.

    Initial studies have shown that the toxin is a small polypeptide that is only 9 amino acids long (see image at right).


    Since each amino acid is coded for by 3 bases of DNA called a triplet (see image at right), a total of 27 bases of DNA, or 9 mRNA codons, codes for the entire toxin polypeptide.

    At this point, the actual amino acid sequence of the polypeptide hasn't been worked out. But DNA has been isolated from the bacteria. Your task is to determine the identity of the amino acids by decoding the DNA sequence that codes for them.

    Once this is known, perhaps a vaccine can be developed to immunize the population.


    To crack the code for the toxin, you're going to need to know some grade 12 biology. DNA, amino acids, mRNA, codons .. that kind of stuff.

    1. Use the "DNA DeCoder" interface to figure out the amino acids from the supplied DNA sequences. You might want to read the Help screen which is opened by clicking '?' on the interface (see image below left).

    2. Use the "Peptide Pro" interface to answer multiple-choice questions (see image below right).

    3. If you can do that, you might just save the human race!

DNA DeCoderPeptide Pro
Play tOXin

Graphics and content by E. Kimmel © 2004