1. Warm Up: November 1, 2013  Homework: None  Due today: Enzyme lab if it was not turned in yesterday  Warm-Up: Fear Factor

2. DNA Replication How DNA makes a copy of itself

3. Eukaryotic Cell Cycle: Mitosis

4. Prokaryotic Cell Cycle: Binary Fission

5. So what is happening basically?

6. Who discovered the double helix?

7. These Guys! Watson and Crick

8. Semiconserative vs. Conservative Model  Watson and Crick’s model predicts that when a double helix replicates, each of the two daughter molecules will have one old strand, derived from the parent molecule and one newly made strand  This can be distinguished from a conservative model of replication, in which the two parent strands somehow come back together after the process, which means that the parent molecule is conserved

9. DNA Replication Models

10. Meselson-Stahl Experiment  3 Theories  Experiment with E. Coli

11. DNA Replication: A Closer Look  The bacterium E. Coli has a single chromosome of about 4.6 million nucleotide pairs  In a favorable environment, it can copy all of its DNA and divide to form two genetically identical daughter cells in less than an hour  Each of your cells has 46 DNA molecules in its nucleus, one long double-helical molecules per chromosome  That represents 6 billion base pairs, or over a thousand times more DNA than is found in a bacterial cell

12. Let’s take an even closer look: Nucleotides The sugar phosphate backbone is comprised of a nitrogenous base, a sugar, and a phosphate group. This makes up a nucleotide.

13. DNA strands run antiparallel to each other The strands run in different directions than one another Both run in a 5’ to 3’ direction Base pairs match up accordingly (A with T, and G with C)

14. Enzymes involved with DNA Replication  Helicase: Unwinds DNA at replication forks  Primase: Synthesizes an RNA primer at 5’ end of leading strand and each Okazaki fragment of lagging strand  DNA polymerase III: Adds nucleotides to the 3’ end of a pre-existing DNA strand or RNA primer  DNA polymerase I: Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides  DNA ligase: Joins 3’ end of DNA that replaces primer to rest of leading strand and joins Okazaki fragments of lagging strand

15. Other important components of replication  Single-Strand Binding Proteins: Bind to unpaired DNA strands  Okazaki Fragments: Short, newly synthesized DNA fragments that are formed on the lagging strand during DNA replication