End Show Slide 1 of 37 Copyright Pearson Prentice Hall 12–1 DNA

End Show 12–1 DNA Slide 2 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Griffith and Transformation 1928 He isolated two different strains of pneumonia bacteria from mice and grew them in his lab. Griffith made two observations: (1) The disease-causing bacteria grew into smooth colonies on culture plates. (2) The harmless strain grew into colonies with rough edges.

End Show 12–1 DNA Slide 3 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Griffith's Experiments Experiment 1: Mice were injected with the disease-causing strain of bacteria. The mice developed pneumonia and died.

End Show 12–1 DNA Slide 4 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Experiment 2: Mice were injected with the harmless strain of bacteria. These mice didn’t get sick. Harmless bacteria (rough colonies) Lives

End Show 12–1 DNA Slide 5 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Experiment 3: Griffith heated the disease-causing bacteria. He then injected the heat- killed bacteria into the mice. The mice survived. Heat-killed disease- causing bacteria (smooth colonies) Lives

End Show 12–1 DNA Slide 6 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Experiment 4: Griffith mixed his heat- killed, disease-causing bacteria with live, harmless bacteria and injected the mice. The mice developed pneumonia and died. Live disease- causing bacteria (smooth colonies) Dies of pneumonia Heat-killed disease- causing bacteria (smooth colonies) Harmless bacteria (rough colonies)

End Show 12–1 DNA Slide 7 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Griffith concluded that the heat-killed bacteria passed their disease- causing ability to the harmless strain. Live disease- causing bacteria (smooth colonies) Heat-killed disease- causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumonia

End Show 12–1 DNA Slide 8 of 37 Copyright Pearson Prentice Hall Griffith and Transformation Transformation Griffith hypothesized that a factor must contain information that could change harmless bacteria into disease-causing ones.

End Show 12–1 DNA Slide 9 of 37 Copyright Pearson Prentice Hall Avery and DNA Oswald Avery repeated Griffith’s work to determine which molecule caused the transformation. When enzymes destroyed proteins, lipids or carbohydrates, transformation still occurred. When DNA was destroyed, transformation did not occur. Therefore, they concluded that DNA was the transforming factor.

End Show 12–1 DNA Slide 10 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Alfred Hershey and Martha Chase studied viruses that can infect living organisms. A virus that infects bacteria is known as a bacteriophage. Bacteriophages contain DNA or RNA and a protein coat.

End Show 12–1 DNA Slide 11 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Bacteriophages A bacteriophage injects its DNA into the bacteria. The viral genes produce many new viruses which eventually destroy the bacterium. When the cell splits open, hundreds of new viruses burst out.

End Show 12–1 DNA Slide 12 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment If Hershey and Chase could determine which part of the virus entered an infected cell, they would learn whether genes were made of protein or DNA. They grew viruses in cultures containing radioactive isotopes of phosphorus-32 ( 32 P) and sulfur-35 ( 35 S).

End Show 12–1 DNA Slide 13 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment If 35 S was found in the bacteria, it would mean that the viruses’ protein had been injected into the bacteria. Bacteriophage with suffur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

End Show 12–1 DNA Slide 14 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment If 32 P was found in the bacteria, then it was the DNA that had been injected. Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium

End Show 12–1 DNA Slide 15 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Nearly all the radioactivity in the bacteria was from phosphorus ( 32 P). Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein.

End Show 12–1 DNA Slide 16 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA is made up of nucleotides: - five-carbon sugar called deoxyribose, - phosphate group, - nitrogenous base.

End Show 12–1 DNA Slide 17 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA There are four kinds of bases in in DNA: adenine guanine cytosine thymine

End Show 12–1 DNA Slide 18 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA The sides (backbone) of DNA are alternating sugars & phosphate groups. The rungs of the ladder are the base pairs. Guanine [G] and cytosine [C] bases are equal. Adenine [A] and thymine [T] bases are equal.

End Show 12–1 DNA Slide 19 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA The Double Helix Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other.

End Show 12–1 DNA Slide 20 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA Double Helix

End Show Slide 21 of 37 Copyright Pearson Prentice Hall 12–1 Avery and other scientists discovered that a.DNA is found in a protein coat. b.DNA stores and transmits genetic information from one generation to the next. c.transformation does not affect bacteria. d.proteins transmit genetic information from one generation to the next.

End Show Slide 22 of 37 Copyright Pearson Prentice Hall 12–1 The Hershey-Chase experiment was based on the fact that a.DNA has both sulfur and phosphorus in its structure. b.protein has both sulfur and phosphorus in its structure. c.both DNA and protein have no phosphorus or sulfur in their structure. d.DNA has only phosphorus, while protein has only sulfur in its structure.

End Show Slide 23 of 37 Copyright Pearson Prentice Hall 12–1 DNA is a long molecule made of monomers called a.nucleotides. b.purines. c.pyrimidines. d.sugars.

End Show Slide 24 of 37 Copyright Pearson Prentice Hall 12–1 Chargaff's rules state that the number of guanine nucleotides must equal the number of a.cytosine nucleotides. b.adenine nucleotides. c.thymine nucleotides. d.thymine plus adenine nucleotides.

End Show Slide 25 of 37 Copyright Pearson Prentice Hall 12–1 In DNA, the following base pairs occur: a.A with C, and G with T. b.A with T, and C with G. c.A with G, and C with T. d.A with T, and C with T.