A Hands-On Approach to Teaching the DNA Structure and FUNCTION 

Carter, Linda                   DuSable High School
                                536-8600
                      

Objective:

To understand the structure of DNA and the way in which DNA duplicates 
by building simple models of DNA and its components.

Apparatus Needed:

Large and small paper clips, 5 cm lengths of colored pipe cleaners, 
styrofoam blocks.

Recommended Strategy:

1. Suggested use of materials:
     Large paper clip to represent deoxyribose sugar
     Small paper clip to represent phosphate group
     Yellow pipe cleaner - adenine base
     White pipe cleaner - thymine base
     Red pipe cleaner - guanine base
     Orange pipe cleaner - cytosine base

2. To form a nucleotide, hook a large paper clip to a small paper 
   clip. Then take a short piece of pipe cleaner and fasten it to the 
   center of the large paper clip. Remember what each of these 
   represents. 

3. Put half of your nucleotides to one side (two of each color). These 
   will be used later as your free nucleotides. Line up the remaining 
   nucleotides in one row and write down their order, then determine 
   what the other side of the ladder would have to be to match. Do 
   this about three times to familarize yourself with the order in 
   which the bases pair.
    
4. Make a flat model of DNA, using the nucleotides you have before 
   you, hook half the clips together (using one of each color), 
   making sure the large and small clips alternate to form one side 
   of the ladder.  Using the four remaining nucleotides, match the 
   bases in proper order, hook the pipe cleaners together and then hook 
   the clips together to form the sides.

5. To show replication, unhook the pipe cleaner bases from each other 
   to form two chains. Now using your free nucleotides that you put to 
   the side, match them in their proper order and fasten the bases 
   and paper clips together to form two DNA molecules. 

6. To make a three-D model, use two pieces of styrofoam and one of 
   the flat DNA models. Straighten out the two paper clips at each end 
   and press them into the styrofoam strips. Hold a styrofoam 
   strip in each hand, stretch out the model, and twist slightly to 
   give a spiral staircase effect. 


Part II: mRNA STRUCTURE and TRANSCRIPTION

Objective

To use the DNA model to build a model of mRNA which will 
demonstrate its structure and the way it is formed by transcription.

Apparatus Needed:

Models from Part 1, the same materials, plus large colored paper clips 
to represent ribose, and green pipe cleaners to represent the uracil 
base.

Recommended Strategy: 

1. Use the materials to form nucleotides of mRNA, at least two of 
   each of the four bases.

2. Use the flat model of DNA from Part 1 and your mRNA nucleotides to 
   demonstrate transcription. Unhook your flat molecule at its bases. 
   Match the mRNA nucleotides in their proper order (keep in mind that 
   thymine is replaced by uracil).

Evaluation          

For a follow up assignment write a report describing the structures 
of DNA and mRNA and the processes of replication and transcription.