DNA Keychains Presentation created by T. Trimpe 2007 http://sciencespot.net/ Presentation was developed for use with DNA Jewelry lesson at http://accessexcellence.org/AE/AEC/AEF/1995/ross_jewelry.html Graphic from http://nanopedia.case.edu/image/dna.jpg

Part 1: Get Your Materials 1. Choose your large beads for the sugar and phosphate molecules that make up the backbone. You will need 26 beads of 2 different colors for a total of 52 beads. Color the key on your DNA Guide. 2. Choose your small beads for the nitrogen bases. You will need 6 beads of 4 different colors for a total of 24 beads. Color the key on your DNA Guide. 3. Get a piece of thick wire from your teacher and bend it in half. 4. Cut a piece of thin wire – 20 inches in length - and bend it in half. 5. Add two SUGAR beads – one on each side – to the THICK wire. 6. Next add two PHOSPHATE beads– one on each side of the wire.

Part 2: Build Your DNA Molecule 7. Place one A bead and one T bead in the middle of the THIN wire. and hold it in place at the top of the phosphate beads. Line up the THICK and THIN wires on each side and hold at the top. 8. Slide one SUGAR bead down one end of the thin wire and thread the thick wire through as you push it towards the bottom of the keychain - both wires are need to be threaded "inside" the large bead . Add another SUGAR bead on the other side in the same way. 9. Slide one PHOSPHATE bead down one end of the thin wire and thread the thick wire through as you push it towards the bottom of the keychain - both wires are need to be threaded "inside" the large bead . Add another PHOSPHATE bead on the other side in the same way. 10. Pull the large beads down towards the bottom of the keychain and pull on the ends of the thin wire to make the small beads fit tightly in place.

Continue building the DNA molecule following the same process. 11. Hold one of the thin wires near the end and add a G bead and a C bead. Thread the end of the other thin wire back through the G and C beads in the opposite direction make the wires form an X shape. Pull the ends as if you were “tying” a knot. Thread the other end of the wire through the little beads in the opposite direction. Pull on both ends of the thin wire to “tie” it together 12. Add more big beads (SUGARS & PHOSPHATES) to the backbone – TWO on each side. Thread the THIN wire through the large beads as you add the big beads to the THICK wire. Continue building the DNA molecule following the same process. Remember the process… Thread two wires through two big beads on the sides, Cross two wires through two small beads in the middle & tie. Remember … Make sure you keep the bases paired correctly – A with T and G with C. Make sure to keep your wires pulled tight as you add all of the bases. Go slow and try not to get kinks in the THIN wire!

Part 3: Finishing the Double Helix 14. Once you have added all the base pairs, twist the ends of the thin wire together tightly and add a key ring to the other end of the keychain. 15. Twist the ends of the thick wire and the thin wires together all at once! 16. Use the wire cutters (pliers) to cut off the ends leaving it ½ inch long. Use the pliers to “tuck” the ends in between the large beads so it won’t poke you. 17. Twist your DNA strand around a pencil or finger and gently pull on the ends to create the double helix shape. CAUTION: Untwisting and twisting your keychain too many times will make it break!

Make A Paper Model When you are done, color the BASES on a paper model of your DNA keychain. Be sure the colors of the bases match exactly!  Write your name on the back of the a paper model.   Turn in your keychain and the paper model to your teacher.

DNA Replication Step 2: “Unzip” the paper model by cutting it in half longwise and glue the pieces in the correct location on your worksheet so the bases match up correctly. Cut in half Step 1: After you have completed your DNA keychain, label the bases on the paper model with A, T, G, or C exactly as they are on your keychain from the bottom to the top.

Step 3: Label the empty boxes using A, T, G, or C and then color them using the colors on your DNA Guide. Remember to match the bases correctly! A – T T – A G – C C - G Step 4: Answer the questions on the back of your worksheet.

1. How do the bases in DNA pair up? Questions 1. How do the bases in DNA pair up? A - _____ G - _____ T - ______ C - ______ 2. Compare your two “new” DNA molecules (the ones you did on the front) to your actual keychain. How does the order of the bases they compare? 3. What do we call a change in a gene or chromosome? ________________ 4. What two cell division processes use DNA replication? _________________ & _________________ 5. What is created by each of the processes in #4? T C A G The order of the bases should match the order on your keychain. Mutation Meiosis Mitosis Meiosis – Sex Cells Mitosis – Daughter Cells

6. What do we call a set of three nitrogen bases? Going Further ... As we discussed in class, the DNA molecules consists of nitrogen base pairs. The order of the pairs determines the genetic code, which controls protein synthesis or the production of proteins. 6. What do we call a set of three nitrogen bases? ___________________ or ____________________ 7. What organelle in a cell contains the DNA? ___________________ 8. What organelle is the protein factory in a cell? __________________ 9. How does the genetic code get to a ribosome? _______________________ 10. What type of RNA assembles the proteins? ________________________ 11. What are the building blocks of proteins? ______________________ 12. What is another term for a protein? ____________________ chain (a natural polymer) Triplet Codon Nucleus Ribosome Messenger RNA (mRNA) Transfer RNA (tRNA) Amino Acids Polypeptide

http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea6.jpg

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