1. DNA Structure
Chapter 8 Section 2

2. What are the parameters for DNA?
DNA must contain information.
DNA information must be heritable or copied.
DNA information must be expressed.
DNA information must be able to change.

3. Erwin Chargaff ( )

4. Rosalind Franklin ( )

5. Maurice Wilkins ( )

6. Francis Crick ( )

7. James Watson (D.O.B. 1928)

8. DNA Deoxyribonucleic Acid
5 carbon sugar (aldopentose)
Nucleic-
located in the nucleus of eukaryotes
Acid-
phosphate group

9. Deoxyribose Sugar

10. Nitrogenous Bases
Chargaff’s Rules: Erwin Chargaff’s data showed that in spite of which organism he study,
their DNA contained adenine (A) and thymine(T) in equal amounts and guanine (G) and
cytosine (C) were also found in equal amounts.

11. Chargaff’s Data

12. DNA: “polynucleotide”
Polymer
Large molecule composed of many repeated subunits.
Monomer
Molecule that may bind chemically to other molecules to form a polymer (a.k.a. “building block”).
Nucleotide
Building block or monomer of DNA.
If the monomer for DNA is a nucleotide then the DNA molecule can be refer to as a polynucleotide.

13. Nucleotide
There are 4 different DNA nucleotides. The difference between one
nucleotide and another depends on the nitrogenous base it
contains.

14. Notice the location of the phosphodiester bond
Notice the location of the phosphodiester bond. The phosphate group is located between the 5’ and 3’ carbons.

15. X-ray crystalographic photograph

16. DNA Structure
DNA is composed of 2 complementary strands of nucleotides.
Base pair rules determine how the two nucleotide strands “fit” together.
adenine (A) always bonds with thymine (T)
cytosine (C) always bonds with guanine (G)
The arrangement of the 2 nucleotide strands is antiparallel, that is they run in opposite directions.
The 2 complementary strands wind around one another like a twisted latter.

17. DNA Structure
Notice the end of the molecule in figure (a): one begins with 3’ carbon the other 5’ carbon.