Download DNA Keychains: Spell Your Initials Using the Genetic Code!!!!! This

DNA Keychains: Spell Your Initials Using the Genetic Code!!!!! Campus Middle School – Center for the Physics of Living Cells Outreach This week in your science class you will be learning about how the DNA code is read by the cellular machinery to make proteins. This is how your genes are expressed to produce the traits you observe! To read the DNA, your cells use the Genetic Code, where every 3 DNA bases code for a certain amino acid. Amino acids are the building blocks of proteins and when you attach them all together in a specific order you get a polymer of amino acids known as a protein! Today, you will use the Genetic Code to spell your name or initials using DNA codons. A codon is one of the sets of 3 DNA bases which code for a certain amino acid. In this case, each codon will represent a letter in your name or initials! The Genetic Code actually has more than one codon for most amino acids because there are only 20 amino acids even though there are 64 (4 x 4 x 4) possible 3-­‐letter codons! Spelling Your Initials: Use the Genetic Code table on the next page to spell your initials or the first 2-­‐4 letters of your name in DNA bases. You will fill in the codons from the table for each letter in strand 1. If there is more than one codon for one of your letters, just choose one. Next, fill in strand 2 based on the known base-­‐pairing present in DNA. Do you remember which bases pair with which? Write them here: Adapted by Sharlene Denos from “DNA Jewelry Models” by Catherine Sheils Ross (see http://accessexcellence.org/AE/AEC/AEF/1995/ross_jewelry.php) 1 Genetic Code One Letter Code Amino Acid Codon A Alanine GAT, GAC, GAA, GAG B none use Alanine codons C Cysteine TGC, TGT D Aspartic Acid GAT, GAC E Glutamic Acid GAG, GAA F Phenylalanine TTT, TTC G Glycine GGT, GGC, GGA, GGG H Histidine CAT, CAC I Isoleucine ATT, ATC, ATA J none use Isoleucine codons K Lysine AAA, AAG L Leucine TTA, TTG, CTT, CTC, CTA, CTG M Methionine ATG N Asparagine GAT, GAC O none use Asparagine codons P Proline CCT, CCC, CCA, CCG Q Glutamine GAG R Arginine CGT, CGC, CGA, CGG, AGA, AGG S Serine AGT, AGC, TCT, TCC, TCA, TCG T Threonine ACT, ACC, ACA, ACG U none use Threonine codons V Valine GTT, GTC, GTA, GTG W Tryptophan TGG X none use Tryptophan codon Y Tyrosine TAT, TAC Z none use Tyrosine codons Adapted by Sharlene Denos from “DNA Jewelry Models” by Catherine Sheils Ross (see http://accessexcellence.org/AE/AEC/AEF/1995/ross_jewelry.php) 2 Designing Your Keychain: To make your keychain, you will need to assign a specific bead color to each base, sugar and phosphate. Choose one of the small bead colors for each DNA base and one of the large bead colors for the backbone sugar and phosphate. List these in the table below: Base Color (use small Backbone Color (use large beads) Molecule beads) A Sugar C Phosphate T G Building Your Keychain: We will get you started with your keychain in class, but you will need to finish it at home. Here are some steps to help you complete your keychain. Adapted by Sharlene Denos from “DNA Jewelry Models” by Catherine Sheils Ross (see http://accessexcellence.org/AE/AEC/AEF/1995/ross_jewelry.php) 3 ***Remember as you work to make sure you always know which side is strand 1 and which is strand 2. If you lose track, check the strand key you made above with the bases already added to your keychain*** 1. If your last bead was a base, then you will need to add a sugar bead. Add a sugar bead to each strand. Make sure to thread BOTH wires through these beads. 2. If your last bead was a sugar, then you will need to add a phosphate bead. Add a phosphate bead to each strand. Make sure to thread BOTH wires through these beads. 3. If your last bead was a phosphate bead, then you will need to add two base beads. Fold one wire from each strand so it is pointing downward and out of the way. Thread the strand 1 base onto the remaining wire for strand 1, then thread the strand 2 base onto the SAME (strand 1) wire. Now thread the strand 2 wire through both beads and pull both wires like you are making a knot (see picture). Make sure the beads are pulled tight or your keychain will not hold up well. Homework Assignment: Turn in your keychain along with this handout. Make sure the DNA strand key above is filled out with your name or initials and that you have answered the question on page 1. Also, write a paragraph summarizing the structure of DNA shown in your keychain model. Make sure to point out what each bead corresponds to in the real molecule! Adapted by Sharlene Denos from “DNA Jewelry Models” by Catherine Sheils Ross (see http://accessexcellence.org/AE/AEC/AEF/1995/ross_jewelry.php) 4