1. Interest Grabber Order! Order! Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message. Section 12-1 1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. 2. Try rearranging the units to form other words. Remember that each new word can have only three units. Write each word on your paper, and then add a definition for each word. 3. Did any of the codes you formed have the same meaning? 4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message? Go to Section:

2. Search for DNA Three major experiments Conclusion- DNA is genetic material in cells

3. Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease- causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment Go to Section:

4. Conclusion Genetic material could be transferred between cells What is that material????

5. Avery’s Experiment Was transforming material protein, RNA, or DNA??? Used enzymes to destroy each material in heat killed S bacteria

6. Conclusion Bacteria missing protein or RNA would transform R cells into S cells. Bacteria missing DNA did NOT transform R cells. DNA is responsible for transformations

7. Hershey-Chase Support Avery’s conclusions Show how DNA and proteins cross cell membranes

8. Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

9. Conclusion Only DNA of viruses enter bacterial cells

10. Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Figure 12–7 Structure of DNA Section 12-1 Go to Section:

11. DNA Deoxyribonucleic acid Double helix (winding staircase) Monomers: nucleotides

12. PurinesPyrimidines AdenineGuanine CytosineThymine Phosphate group Deoxyribose Figure 12–5 DNA Nucleotides Section 12-1 Go to Section:

13. DNA Structure Chargaff- A = T and G = C (Info used to determine base pairing) Franklin & Wilkens- x-ray diffraction images showed tightly coiled helix of 2 or 3 chains of nucleotides **Watson & Crick- Created 3-D image of DNA