1. DNA

2. Discussion Questions What is DNA? What does it do? How does it do it?
Chargraff’s Data Worksheet
Read WS Introduction Silently
Chargraff’s Data Worksheet Analysis Q’s 1-5

3. DNA is a molecule present in the nucleus of all cells in all living organisms

4. DNA directs protein synthesis
DNA controls all the chemical changes which take place in cells
DNA directs protein synthesis

5. The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA

6. The kind of organism which is produced (buttercup, giraffe, guppy, monkey etc) is controlled by DNA
So….. what is DNA?

7. There are four types of nitrogenous bases.

8. Each base will only bond with one other specific base.
Adenine (A) Thymine (T)
Guanine (G) Cytosine (C)
The bases are held together by weak Hydrogen (H) bonds

9. The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”.

10. DNA is a very large molecule made up of a long chain of sub-units
DNA is a very large molecule made up of a long chain of sub-units. The sub-units are called nucleotides. Each nucleotide is made up of a sugar called deoxyribose a
phosphate group, and a nitrogenous base.

11. In 1953, James Watson and Francis Crick shook the world with an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA

12. Genetic information is carried in the linear sequence of nucleotides in DNA. Each molecule of DNA is a double helix formed from two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs. Duplication of the genetic information occurs by the use of one DNA strand as a template for formation of a complementary strand. The genetic information stored in an organism’s DNA contains the instructions for all the proteins the organism will ever synthesize.

13. What are Chargaff’s Rules?
Chargaff's rules states that DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine.

15. HW: Watch this video to get a better understanding of the DNA molecule
Nucleic acids (Bozeman Science video)