1. DNA, RNA and DNA Replication IB Biology 2011-2012

2. DNA History: DNA as Genetic Material Griffith: Pneumonia and Mice (1928)

3. DNA History: DNA as Genetic Material Hershey & Chase

4. DNA History: DNA as Genetic Material Watson & Crick

5. DNA is a nucleic acid, made of long chains of nucleotides Structure of DNA Nucleotide Phosphate group Nitrogenous base Sugar PolynucleotideSugar-phosphate backbone DNA nucleotide Phosphate group Nitrogenous base (A, G, C, or T) Thymine (T) Sugar (deoxyribose)

6. DNA has four kinds of bases, A, T, C, and G Pyrimidines Thymine (T)Cytosine (C) Purines Adenine (A)Guanine (G)

7. RNA is also a nucleic acid –RNA has a slightly different sugar –RNA has U instead of T Phosphate group Nitrogenous base (A, G, C, or U) Uracil (U) Sugar (ribose)

8. Three representations of DNA Ribbon modelPartial chemical structureComputer model Hydrogen bond

9. Representation of DNA: Chromatin to Chromosome

10. Chargaff’s Rule In DNA replication, the strands separate – Enzymes use each strand as a template to assemble the new strands DNA Replication: DNA replication depends on specific base pairing Parental molecule of DNA Both parental strands serve as templates Two identical daughter molecules of DNA Nucleotides A A

11. DNA replication begins at specific sites DNA Replication Parental strand Origin of replication Bubble Two daughter DNA molecules Daughter strand

12. Each strand of the double helix is oriented in the opposite direction 5 end3 end 5 end P P P P P P P P

13. How DNA daughter strands are synthesized 5 end P P Parental DNA DNA polymerase molecule 5 3 3 5 3 5 Daughter strand synthesized continuously Daughter strand synthesized in pieces DNA ligase Overall direction of replication 5 3 The daughter strands are identical to the parent molecule