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1 Genes are made of DNA (11.1) Objectives 1. Describe Griffith's experiments and conclusion. 2. Describe Avery's experiments and conclusion. 3. Explain.

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Presentation on theme: "1 Genes are made of DNA (11.1) Objectives 1. Describe Griffith's experiments and conclusion. 2. Describe Avery's experiments and conclusion. 3. Explain."— Presentation transcript:

1 1 Genes are made of DNA (11.1) Objectives 1. Describe Griffith's experiments and conclusion. 2. Describe Avery's experiments and conclusion. 3. Explain how experiments with viral DNA further supported Avery's conclusion. Key Terms virus bacteriophage

2 Griffith's "Transforming Factor" Is the Genetic Material - Griffith showed that although a deadly strain of bacteria could be made harmless by heating it, some factor in that strain is still able to change other harmless bacteria into deadly ones. He called this the "transforming factor."

3 Avery Shows DNA Is the Transforming Factor -To test whether protein was the transforming factor, they treated Griffith's mixture of heat-treated deadly strain and live harmless strain with protein- destroying enzymes, then DNA destroying enzymes.

4 Virus Experiments Provide More Evidence -In 1952, biologists Alfred Hershey and Martha Chase conducted a series of experiments using viruses. -virus: package of nucleic acid wrapped in a protein coat that must use a host cell's machinery to reproduce itself -bacteriophage: virus that infects bacteria; also called a "phage"

5 Virus Experiments Provide More Evidence -When only phage protein coats were labeled, most of the radioactivity was detected outside the cells. But when phage DNA was labeled, most of the radioactivity was detected inside the cells. - Hershey and Chase offered further evidence that DNA, not proteins, is the genetic material. Only the DNA of the old generation of viruses is incorporated into the new generation.

6 6 Concept Check How did Griffith's experiments indicate the presence of a "transforming factor" in bacteria? 2. What did Avery's experiments add to the knowledge gained from Griffith's experiments? 3. Describe the experimental design that allowed Hershey and Chase to distinguish between the two options for genetic material.

7 7 Nucleic acids store information in their sequence of chemical units. (11.2) Objectives Identify the building blocks of DNA. Describe DNA's structure and the rules for base pairing in DNA. Key Terms deoxyribonucleic acid (DNA) nucleotide nitrogenous base pyrimidine purine double helix

8 The Building Blocks of DNA -deoxyribonucleic acid (DNA): molecule responsible for inheritance; nucleic acid that contains the sugar deoxyribose -nucleotide: building block (monomer) of nucleic acid polymers. (Contains 3 parts) 1.A ring-shaped sugar called deoxyribose 2.A phosphate group 3.A nitrogenous base: a single or double ring of carbon and nitrogen atoms with functional groups.

9 Nitrogenous Bases -The bases thymine (T) and cytosine (C) are single-ring structures called Pyrimidine -Adenine (A) and guanine (G) are larger, double-ring structures called Purines Figure 11-6 DNA contains four different nitrogenous bases. Thymine and cytosine have single-ring structures. Adenine and guanine have double-ring structures.

10 DNA Strands -Nucleotides are joined to one another by covalent bonds that connect the sugar of one nucleotide to the phosphate group of the next. -sugar-phosphate "backbone.“ Figure 11-7 Nucleotide monomers join together by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone.

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12 DNA's Structure The Double helix and Complementary Base Pairs p.231 -double helix: two strands of nucleotides wound about each other; structure of DNA Figure 11-8 The bases pair up between the two intertwined sugar-phosphate backbones, forming the double helix discovered by Watson and Crick. A pairs with T, and G pairs with C.

13 13 Concept Check What are the three parts of a nucleotide? Which parts make up the backbone of a DNA strand? 2. List the two base pairs found in DNA. 3. If six bases on one strand of a DNA double helix are AGTCGG, what are the six bases on the complementary section of the other strand of DNA?


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