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Biology-Mr.Willets
Lab- DNA Model
DNA is the most important molecule associated with life. It is also the largest. To better see how it is put together, we will use a kit to make a model of the DNA molecule. This lab is a fun lab. There is nothing to hand in. You get credit just for being here and doing it. You lose credit for fooling around!!
The model kit we will use is not perfect (what is?) but it will have to do. Each kit should contain all the parts necessary to make the model but it is likely that you will be missing something. If so, ask your friendly teacher for replacement parts. There is a parts list below.
The black pieces with three extensions and a hole in the middle represent deoxyribose sugar. The red pieces with two extensions and a hole represent phosphate. The yellow "straws" are used to join them.
Join six sugars with six phosphates using the yellow straws to connect them. Alternate sugar and phosphate. Make another piece just the same. These are the two sides of your DNA ladder. Straighten them as much as possible but notice that the phosphates stick out from the sugars. This is how the DNA molecule is actually arranged.
There are 4 different colored straws each about 1/2 inch long (in addition to the yellow): blue, red, green and grey. These represent the 4 nitrogen bases. If this kit were accurate, these pieces would fit together in only one way. Since they can be put together lots of ways, we will have to be careful to do it correctly.
We will use the blue to represent adenine and the grey to represent thymine. The red will be cytosine and the green will be guanine. Some of these straws may be cracked. If so, see me.
The white pieces with two extensions are the hydrogen bonds that hold the bases together. Attach a blue straw to one side of the white piece and a grey straw to the other side. Do the same with the other straws to make six base pairs. (red with green: blue with grey) These will be the rungs (steps) of the DNA ladder.
Use these base pairs (rungs) to connect the two sides of your ladder. As you know, they connect at the sugars. At this point, the ladder is not twisted. Find the black plastic piece with four extensions. Attach the three medium length green straws to it. This forms the base of the stand for our model.
Take the long straw and insert it through the holes in the white pieces. One end of this straw should be attached to the stand base. The end of the DNA at the top should have the phosphates on it.
Once the long straw is in place, the whole model can be twisted to form the double helix. Twisting it will be necessary to get the long straw through all of the white pieces. You should twist clockwise from the top. At this moment, you should stand back, admire your work and say "AH! I UNDERSTAND!"
NOW COMES THE REAL FUN PART!!!
When your neighbors have completed their model, you can attach them together to make a longer piece of DNA. You will need a few extra pieces to do this. For these extra pieces and advice see your friendly teacher.
Clean Up- When it comes time to clean up, each kit should have the following pieces:
12 sugars (black / 3 extensions
12 phosphates (red / two extensions)
7 hydrogen bonds (white / 2 extensions)
1 black base with three medium length grey "straw" legs
1 long straw 3 each: blue straws, gray straws, red straws, green straws
26-28 yellow connector straws
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