1. Chapter 12 DNA Structure and Replication

2. Transformation Changes one form of bacteria into a different or some cases toxic form of bacteria EX: Griffith’s experiment with heat killed bacteria vs. a harmless strain

3. Hershey – Chase Experiment Bacteriophages – virus that infects bacteria by attaching to the surface and injecting its DNA into the cell. -genes produces more copies of bacteriophages and destroy the cell

4. Components of DNA Nucleotide is monomer of DNA consisting of a 5 carbon sugar, phosphate, and a nitrogen group

5. Purines vs. Pyrimidines Purines are structures with 2 rings Ex: adenine & guanine Pyrimidines have 1 ring Ex: cytosine & thymine

6. Base Pairing

7. Double Helix DNA is a twisted ladder or spiral staircase. -Sugar phosphate backbone forms outside braces to the ladder -Nitrogen base pairs are the steps held together by hydrogen bonds.

8. Chromosomes Prokaryotes – DNA is circular and fills most internal space of organism, cytoplasm - no internal organelles Eukaryotes – nucleus holds DNA Length of DNA in both types of organisms is vast. Eukaryotes have about 1000 times more base pairs.

9. Structure of Chromosome Chromatin is the structure formed from tightly coiled DNA and proteins -consists of nucleosome (protein) that packs DNA around histones in a beadlike thread.

10. DNA Replication What phase of cell cycle will DNA duplicate itself? During S phase DNA will separate and enzymes will aid in the copying mechanism that give a complementary strand from each DNA template strand

11. Replication Steps of Replication: 1.Enzymes unzip the DNA molecule and breaks hydrogen bonds 2.Each strand serves as a template for complementary (matching) strands 3.An enzyme joins and proofreads sequence 4.Enzymes patch together any gaps in sequence for new strand

12. DNA Replication

14. Enzymes of Replication DNA Helicase is the enzyme responsible for untwisting the DNA DNA Polymerase is the enzyme responsible for base pairing and proofreading the complementary nucleotides in the new copied strands DNA Ligase patches and connects all spaces between sequences.

15. Antiparallel Recognition Antiparallel meaning sequences are matching in opposite directions, or oriented in different directions Ex: 3’ GGTTAACCGATC 5’ 5’ CCAATTGGCTAG 3’

16. EXIT QUESTION What are the steps of DNA Replication?