1. Bell Ringer 3.21 1.What are the 3 major components of DNA? 2.What are the four nitrogenous bases of DNA? 3.What bonds link together these nitrogenous bases? 4.What are the “backbones” of our DNA made of? 5.Where is DNA located?

2. Bell Ringer 3.21 1.Phosphate group, sugar, & nitrogenous base. 2.Adenine, guanine, cytosine, & thymine. 3.Hydrogen bonds.. (A  T 2) (C  G 3) 4.Alternating phosphates and sugars. 5.Nucleus

3. DNA Replication

4. DNA Replication = how DNA copies itself Occurs just before mitosis and meiosis during interphase. Occurs at many different spots along DNA at the same time.

5. Replication Steps 1.Begins when the enzyme DNA Helicase attaches to the DNA and begins to “unzip” it by breaking hydrogen bonds. 2.Strands are separated, the unpaired bases react with free nucleotides in the nucleus 3.The free nucleotides attach forming new hydrogen bonds, enzyme DNA polymerase connects the new nucleotide strand with sugar-phosphate bonds.

6. Result 2 new DNA molecules identical to the original. Each new DNA contains one old strand and one new strand of nucleotides = semi-conservative process Many other enzymes are involved to help “proofread” to ensure accuracy

8. Practice Write the complementary strands for the following template strands: 1.ACG TTA CGC TCG CTG 2.AAC ATC CGT ATC ATG 3.ATA GGC CGA TGC AGC

9. Check List… 1.Group Review (Smart Board) 2.DNA Replication W/S (groups 3) 3.Finish Paper Lab (Friday) 4.Cell Membrane (grading TODAY!) 5.Molecular Genetics Unit Guide (vocab & questions)