LS: I will be able to explain the process of DNA replication.

The Basics: 1) A single strand of DNA serves as a template for a new strand 2) DNA is replicated during S phase of the cell cycle 3) Each body cell gest a complete set of identical DNA Replication = Copying ?v=FBmO_rmXxIw

Replication is fast and accurate DNA serves only as a template Enzymes and other proteins do the actual work of replication DNA replication starts at many points in eukaryotic chromosomes Enzymes Involved: 1) RNA primase 2) DNA helicase 3) DNA gyrase (mainly bacteria) 4) DNA polymerase I 5) DNA polymerase III 6) DNA ligase The process of replication:

1. DNA strands are unzipped at the points of origin by DNA helicase (site is known as the replication fork) 1. In bacteria, DNA gyrase is added to reduce the tension in the coiling of the DNA strands 2. RNA primase is added 1. Identifies where the new nucleotides need to be added 2. Both strands are used as templates, but constructed in opposite directions What are the steps of replication? Opposite directions = antiparallel

3. DNA polymerase III adds and binds new nucleotides to the growing DNA chain 4. The DNA strands are checked for accuracy by DNA p0lymerase I 5. The gaps are then corrected by DNA ligase What happens next?

DNA Replication follows the Semi-Conservative model Which means: Each strand of DNA will act as a template for the synthesis (“making of”) of a new DNA molecule, following the base pairing rule THEREBY CREATING 2 NEW DNA MOLECULES THAT EACH HAS ONE OF THE ORIGINAL STRANDS AND ONE NEW STRAND Semi-Conserva-a-what?

1. The enzyme ____________ unzips the double helix. 2. RNA ______________ identifies where replication begins 3. DNA _________________ binds free floating nucleotides to the template strand. 4. DNA _________________ forms bonds between the two strands. 5. DNA _________________ proofreads the new strands, and makes any corrections. 6. DNA ____________ fills in any gaps on the developing DNA strand. Let’s RECAP- The steps of replication: