Discovering the Structure of DNA

NAME:______

Discovering the Structure of DNA

1. What do the letters DNA stand for?

2. DNA is a polymer, which means that is made up of many repeating single units (monomers). What

are the monomers called?______

3. Look at your nucleotide and the nucleotides of the other members of your group. What are the three common parts of a nucleotide?

a.

b.

c.

4. What is one part of the nucleotide that differs among the four different nucleotides in your group? (these are called bases)

5. There are four different variations of these monomers (four different bases), what are the names of

those bases?

a.

b.

c.

d.

6. Manipulate the nucleotide pieces until you find the best fit. Join the nucleotide molecules in your group together like a puzzle. Use tape to connect and reinforce the molecules. You now have a molecule of DNA.

7. In the space below, explain where the nucleotide molecules connect to each other.

8. A real DNA molecule consists of THOUSANDS of these pairs of nucleotides. What is the pairing arrangement of nitrogen bases?

______pairs with ______and ______pairs with ______

This is called complementary base pairs. Thus one strand of DNA is complementary to the other

strand (opposite/matching).

9. The “backbone” of the DNA molecule is made up of two components, what are these?

c. ______

d. ______

10. DNA of any species contains equal amounts of ______and ______and also equal amounts of ______and ______.

11. Explain why there will always be an equal amount of adenine and thymine and guanine and cytosine.

12. Write the complementary sequence to following DNA strand:

A A T T C G C C G G T A T T A G A C G T T

| | | | | | | | | | | | | | | | | | | | |

13. These bases are of two different types of molecules: purines and pyrimides. Purines have

______ring(s) in their structure, and pyrimidines have ______ring(s) in their structure.

14. The two bases that are purines are:

a. ______

b. ______

15. The two bases that are pyrimidines are:

a. ______

b. ______

16. Use the image at the right to complete the follow:

Circle a nucleotide.

Label the sugar and phosphate.

Label the bases that are not already labeled

Label where the hydrogen bonds exist

17. The structure of DNA is actually in a DOUBLE HELIX arrangement. This means that the two long chains of nucleotides are arranged in a spiral like a twisted ladder.

18. The sides (or “uprights”) of the ladder are made up of alternating ______and ______molecules. The steps (or “rungs”) of the ladder are made of ______held together by HYDROGEN BONDS.

19. Bring your molecule to the front of the room (with all of your names on it) and join it to the molecules of the other groups. We now have one large DNA molecule.