Interest Grabber. Section 12-1. 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.
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Interest Grabber Section 12-1 • 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. 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 eachnew 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:
Search for DNA • Three major experiments • Conclusion- DNA is genetic material in cells
Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Harmless bacteria (rough colonies) Control(no growth) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies) Go to Section:
Conclusion • Genetic material could be transferred between cells • What is that material????
Avery’s Experiment • Was transforming material protein, RNA, or DNA??? • Used enzymes to destroy each material in heat killed S bacteria
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
Hershey-Chase • Support Avery’s conclusions • Show how DNA and proteins cross cell membranes
Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium Go to Section:
Conclusion • Only DNA of viruses enter bacterial cells
Figure 12–7 Structure of DNA Section 12-1 Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Go to Section:
DNA • Deoxyribonucleic acid • Double helix (winding staircase) • Monomers: nucleotides
Figure 12–5 DNA Nucleotides Section 12-1 Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose Go to Section:
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