Science


 * DNA** **Jewelry**

INTRODUCTION: DNA, or Deoxyribonucleic Acid, is the genetic material found in every living cell on Earth and, as such, can be called the basic building block of life. In 1953, James Watson and Francis Crick unveiled their discoveries on the structure of DNA in their double helix model.

The aim is to construct the Watson and Crick double helix DNA model by making DNA jewellery.
 * AIM:**

• 1 Small tray • Beads (4 colours of long beads, 2 colours for short beads) • Wire (0.7)
 * MATERIALS** (per student):


 * Preparation**

Four different coloured long beads will be provided for you. You must decide which colour represents which base. Remember that adenine always pairs with thymine, and guanine always pairs with cytosine. Choose a different colour for each base.

The sugar and phosphate groups will be represented by round beads, the bases by long beads.

Complete the following table You must show your completed chart to your teacher for assessment and verification before you start making the model.
 * DNA base || Bead Colour || DNA base || Bead Colour ||
 * Cytosine ||  || Guanine ||   ||
 * Thymine ||  || Adenine ||   ||
 * Phosphate ||  || Deoxyribose sugar ||   ||
 * Phosphate ||  || Deoxyribose sugar ||   ||

Open the file to see diagrams that explain how to make the DNA model.


 * Step 1**

Measure out 86 centimeters of 28 gauge wire. Find the mid-point and place the beads at the halfway point in the manner shown in Figure 1. During this, and all following operations, be careful not to put "kinks" in the wire because that will weaken the wire and make it difficult to thread through the narrow openings in the tubular bugle beads.


 * Step 2**

Run the end of the wire on the right through the beads on the left. Run the end of the wire on the left through the beads on the right.


 * Step 3**

Double check that the beads are in the centre of the wire. Pull the wires gently to snug up the beads against each other. They should look like the photo below.


 * Step 4**

Add a phosphate and a deoxyribose to the right and left wires. Add your choice of one of the matching nitrogen bases to each wire. Remember that adenine pairs with thymine, and guanine pairs with cytosine. Cross the wires, and gently remove the slack in the wire as you did before

Repeat until you have 20 base pairs!