A Genetic Code Game

The DNA Part

You will be given a short sense DNA strand nucleotide sequence. This is one strand of the double helix DNA molecule. You will need to find the complement antisense strand. Remember that an A nucleotide pairs with a T nucleotide (A-T) and the C nucleotide pairs with a G nucleotide (C-G). In your journal write down the sense DNA sequence and its antisense (complement). Example :

         Sense DNA strand = GGACTTTGC
                            |||||||||
     Antisense DNA strand = CCTGAAACG

The mRNA Part

In the cell nucleus, the DNA is unraveled with the help of many proteins. A messenger RNA molecule (mRNA) is then created. The DNA will stay in the nucleus, but the mRNA can travel out into the cell. The mRNA is assembled nucleotide by nucleotide from the sense DNA strand. This means the nucleotide sequence is almost identical to the DNA antisense strand with one exception; The mRNA substitutes the nucleotide Uracil (U) for Thymine (T). In your journal write down the sense DNA strand and the mRNA strand created. Example:

          Sense DNA strand = GGACTTTGC
               mRNA strand = CCUGAAACG

The Protein Part

After the mRNA leaves the nucleus it can assemble proteins with the help of large protein and another type of RNA; these are the ribosome and transfer RNA (tRNA). The mRNA, a ribosome and many tRNA work together to make a protein. Remember a protein is a long sequence of smaller molecules stuck together. These smaller molecules are amino acids. There are over twenty amino acids so a single mRNA nucleotide (an U, C, G, or A) isn't enough to tell the ribosome and tRNA which amino acid to use. The ribosome and tRNAs look at three mRNA nucleotides at a time. Each group of three is called a codon.

To figure out which amino acid is specified by a codon (a group of three mRNA nucleotides) you will use the decoder table. Start with the first three mRNA nucleotides and find the name of the amino acid that will be the first part of the protein.

Example: CCU = proline

Repeat the process for the rest of the mRNA.

Example: GAA = glutamate ACG = threonine

For our example, the sense DNA strand encodes for a very short protein = proline + glutamate + threonine. Most proteins are hundreds of amino acids long. Rather than write down the entire name of an amino acid, biochemists use single letter abbreviations. In the decoder table that is the single capital letter following the amino acid name. Example : The amino acid sequence that makes our very short protein would be abbreviated as PET.

The "Game" Part

When decoded properly your DNA strand spells a word. What is that word?