1. DNA Structure & Replication 7.1

2. Hershey & Chase 0 Scientists that proved DNA, not protein, was the genetic material of cells. 0 Used viruses and radioactive isotopes to mark virus proteins and DNA. Supernatant=Light, liquid portion that included the virus protein, not DNA.

3. Rosiland Franklin 0 Used X-ray diffraction to study the structure of DNA. 0 When X-rays are directed at materials, some rays pass through, but others are reflected depending on structure of material. 0 DNA created a clear cut pattern, and her work helped determine the structure of DNA.

4. Watson & Crick 0 Credited with the modern model of DNA. 0 Purines (A & G) always pair with Pyrimidines (T & C). 0 A&T pair up because of differences in charge, C & G pairing creates 3 hydrogen bonds, giving stability. 0 Strands run antiparallel, with information running different directions.

5. Reading DNA 0 DNA strands have a 3’ (3 prime) and a 5’ (5 prime) end. 0 DNA is read from the 3’ end to the 5’ end. 0 DNA replication occurs in a 5’ to 3’ direction.

6. DNA Packaging 0 Eukaryotic DNA utilizes proteins called histones to pack large amounts of DNA into the nucleus. 0 DNA wraps around a set of 8 histones, called an octamer, to form a nucleosome. 0 A special histone, H1, locks the DNA around the octamer.

8. Leading and Lagging 0 Since DNA is antiparallel, each strand’s bases are read in different directions. 0 When a replication fork is formed, replication occurs in different directions. 0 The leading strand of DNA is the strand that runs 3’ to 5’, the lagging strand runs 5’ to 3’. Lagging Strand Leading Strand

9. Ozaki fragments are pieces of new DNA synthesized following the lagging strand.

10. Enzymes 0 DNA helicase is the enzyme responsible for unwinding DNA at replication fork. 0 DNA gyrase or topoisomerase is the enzyme responsible for relieving stress placed on DNA ahead of replication fork. 0 DNA primase creates sections of RNA to start replication. 0 DNA polymerase I is responsible for replacing the RNA primers with DNA. 0 DNA polymerase III is responsible for creating new DNA strands after the RNA primer. 0 DNA ligase joins the fragments of DNA together.

11. Telomeres 0 Repetitive junk DNA found at the ends of chromosomes. 0 As DNA is replicated, telomeres decrease in length, so they are responsible for ensuring the essential DNA is kept.