1. The History & Structure of the DNA Molecule CHAPTER 10 PART 1

2. The History of the DNA Molecule The Impossibility of Information The DNA molecule is one of the greatest scientific discoveries of all time. First described by James Watson and Francis Crick in 1953, DNA is the famous storehouse of genetics that establishes each organism's physical characteristics.

3. DNA History Griffith – Experimented on mice and observed some harmless strains of bacteria could change into harmful strains. He called this transformation. Avery – Discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation to the next.

5. More DNA History Hershey-Chase – Concluded that the genetic material in bacteria was DNA not proteins http://highered.mcgraw- hill.com/olc/dl/120076/bio21.swf http://highered.mcgraw- hill.com/olc/dl/120076/bio21.swf Watson & Crick – created the double helix model for DNA.

8. Nucleotides 1. DNA is made up of subunits which scientists called nucleotides. A nucleotide is a chemical compound that consists of 3 portions: a nitrogenous base, a sugar, and one or more phosphate groups.

9. DNA's structure. 1. There are 4 different bases in a DNA molecule: a.adenine (a purine ) b.cytosine (a pyrimidine ) c.guanine (a purine) d.thymine (a pyrimidine) PURINES - nitrogenous bases that have a double ring of carbon and nitrogen atoms PYRIMIDINES - nitrogenous bases that have a single ring of carbon and nitrogen atoms

10. Base Pairing Rules Chargaff’s Rules In DNA, Cytosine on one strand always pairs with Guanine on the opposite strand. Adenine always pairs with thymine

11. DNA Replication

12. How DNA Replication Occurs DNA replication is the process by which DNA is copied in a cell before a cell divides by mitosis, meiosis, or binary fission.

13. How It Occurs DNA replication is carried out by a series of enzymes. The enzymes unzip the DNA molecule creating two strands that serve as templates. (helicase enzyme moves along DNA molecule breaking the hydrogen bonds) The Y- shaped region the results when the two strands separate is called a replication fork

14. Complimentary bases are added to the strands by enzymes called DNA Polymerase that are found floating freely inside the nucleus, for example a strand of DNA with the bases ATTCGAG would have a complimentary strand of TAAGCTC

15. Each new DNA molecule has one new stand and one strand from the original molecule. (this is called semi-conservative replication) The enzyme DNA polymerase, the principal enzyme, “proofreads” the new DNA strands, helping to maximize the odds that each molecule is a perfect copy of the original. DNA polymerase Finish replicating the DNA and fall off http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=related

17. DNA REPLICATION http://www.youtube.com/watch?v=8kK2zwj RV0M http://www.youtube.com/watch?v=8kK2zwj RV0M