Name _______________________________________
Section 8.2: Structure of DNA
Date __________________
Main Ideas:
 DNA is composed of four types of nucleotides
 The order of the nucleotides is the genetic code
 Scientists worked to develop an accurate model of DNA
 Nucleotides usually pair up in the same way
Vocabulary:
 DNA

Nucleotide

Base pairing rules
At the completion of this section, you should be able to explain what exactly is DNA. How DNA stores
genetic information and the structure of DNA.
1. Look on page 225 at the photo of the glowing mouse. How was this accomplished?
2. What are the monomers (smaller repeating units) that make up DNA (and RNA)? __________________
3. Identify the three parts of all of the answer to #2.
a. __________________________________
b. __________________________________
c. __________________________________
4. Label the nucleotide shown below
5. How many different nucleotides could be found making up DNA? ____________
6. Identify the DNA nucleotides.
a. _____________________________
b. _____________________________
c. _____________________________
d. _____________________________
7. Erwin Chargaff’s contribution to the discovery of DNA’s structure was that the amount of the nitrogen
base adenine = the amount of _____________________. And the amount of the nitrogen base cytosine
= the amount of __________________________. This is known as Chargaff’s rule.
8. Math time!! If a strand of DNA contains 20% of the nitrogen base adenine, then it contains ____% of
thymine. Now add up what you have = ____%. Subtract that from 100% = ____%. Divide this by 2 =
____%. This is the percent of guanine and ___________________________.
9. What did Rosalind Franklin figure out from the X-ray photograph of DNA shown below?
10. Who are the two scientist who built the first 3D model of DNA, using the information from other
scientists (especially Rosalind Franklin’s image from above) _________________ & ______________.
11. Franklin, Watson and Crick all described DNA structure as being a double ________________.
12. If one side of DNA had the nitrogen base sequence of CATGGATAT, the other, complementary strand
would have the sequence __________________________. (Remember to use the rules of base pairing)
13. What type of strong bond holds the DNA nucleotides together? ____________________
14. ______________________________ & _____________________ are the molecules that alternate,
forming the sides of the DNA strands. In the middle, attached to the sugars, will be the ____________
bases, held together by ______________ bonds.
15. Label the diagram below of a short piece of DNA.
Type of bond
Type of bond