Name ________________________________________ Period _________
Modeling DNA Structure
Background:
A DNA molecule looks like a twisted ladder. A DNA molecule is made up of chains of sugar groups
and phosphates connected by pairs of nitrogen bases. There are four nitrogen bases. The letters A,
T, C, and G stand for the four different bases.
Materials:
Scissors, White, purple, green, red, blue, and yellow paper, Tape
Procedure:
1. Cut out 12 white sugar molecules and 14 purple phosphate molecules. Label the molecules.
2. Cut out 12 nitrogen bases as follows: 3 green A’s, 3 red T’s, 3 yellow C’s and 3 blue G’s.
3. Using the small squares and stars as guides, construct the two sides of the DNA molecule
with the sugar and phosphate.
 There will be a trick to creating the complementary backbone of your DNA!!!
4. Complete the molecule of DNA by fitting base pairs within the sugar-phosphate backbones.
5. Tape the entire DNA molecule together. Please use the tape conservatively!!!
6. Your finished model should look like a ladder.
Observations
1. Which 2 molecules of a nucleotide form the sides of a DNA ladder? ______________________
2. What molecules make up the rungs of the DNA ladder? _______________________________
3. What nitrogen base always pairs up with A? ______________________
4. Which base pairs up with G? ______________________
5. Challenge: If 30% of a DNA molecule is Adenine, what percent is Cytosine? ________________
Questions
1. COMPARE Does your DNA model have the same shape and general pattern as those of your
classmate? Explain your answer. ______________________________________________
_______________________________________________________________________
2. Are all DNA models exactly the same? If not, what are the differences? ________________
_______________________________________________________________________
3. MODEL What do you need to do to your model to make it look like a DNA molecule? _________
_______________________________________________________________________
Going Further
Construct a model of a large DNA molecule by taping all the models in the class together. This
large DNA molecule will help you understand better how complex a DNA molecule is.
PICTURES FROM WHEN I HAVE STUDENTS MODEL DNA REPLICATION