Word of the Day Hydrogen Bonds: –Weak bonds that hold the bases of DNA together

History of DNA Milestones

1869: Johann Friedrich Miescher Identifies an acidic substance, of unknown function, in the nuclei of human white blood cells. Calls it DNA

1924 DNA and proteins are present in the cell’s nucleus. Which one is the genetic information? No one knows!

1944: Oswald Avery Identifies DNA as the genetic material Most scientist did not believe that it was the genetic material because DNA is so simple

1949: Erwin Chargaff finds that the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine in DNA from every species.

1951: Rosalind Franklin What did this picture show her?

1953: James Watson and Francis Crick discover the molecular structure of DNA

DNA Structure:

1991: Human Genome Project Goal: to map out the human genes

Information Set #1 *DNA is a polymer. A polymer is a very long, chainlike molecule made of smaller sub unit molecules. *These subunits are like links in a chain. *They are attached by covalent bonds *Four different subunits exist.

Information Set #2 *DNA consists of two long chains of these 4 subunits * The subunits each have a sugar, a phosphate and a base - called a nucleotide *These chains are twisted around each other in a double helix. (A helix is the shape a pipe cleaner takes when it is twisted around a pencil) * The two chains are held together with weak hydrogen bonds at the bases.

Information Set #3 *The order of the subunits in one strand determine the order of the subunits in the other strand. *The sugar and phosphate form a “backbone” to the polymer.

Assignment: Poster Title Vocab List Paragraph describing structure

Vocabulary words Nucleotide Nitrogen bases Chargaff’s rules Double helix Hydrogen bonds Sugar phosphate