1. DNA

2. Characteristics of DNA 1. Supplies instructions for cell processes, like how to make proteins 2. Can be copied each time a cell divides 3. It is the “blueprint of life”, every living thing has DNA

3. DNA Structure Is a nucleic acid that is double stranded Made up of subunits called nucleotides

4. A nucleotide consists of 3 parts: 1. Phosphate 2. Sugar 3. Nitrogen base: adenine (A), guanine (G), thymine (T), cytosine (C) Base (A, T, G, C) Sugar Phosphate

5. Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Structure of DNA Section 12-1

6. Finding DNA’s Shape: the Double Helix Scientific Contributions: 1. Rosalind Franklin: showed DNA was a spiral shape by using X rays 2. Chargaff’s rule: A pairs with T, G pairs with C One strand reads: T C G A A C T The other reads: AAGTTCG

7. Scientific Contributions Cont. 3. Watson and Crick: made a model of DNA structure in 1953 The “Double Helix” looks like a twisted ladder Sides of the ladder are alternating sugar and phosphate units Rungs are the bases held together by hydrogen bonds

8. DNA Replication Def: Ability of DNA to make an exact copy or a new strand of DNA from an old one

9. The Steps in Replication 1. Start with a DNA molecule 2. Hydrogen bonds break and the strands separate (unzip) 3. Add matching nucleotides 4. The result: 2 identical DNA molecules ½ old strand, ½ new strand

10. Drawing DNA Replication: Step 1

11. Drawing DNA Replication: Steps 2 and 3

12. Drawing DNA Replication: Step 4

13. DNA Replication:

14. Chromosomes Tight coils and supercoils of DNA and protein

15. Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

16. Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

17. Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

18. Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

19. Chromosome Supercoils Coils Nucleosome DNA double helix Section 12-2