Biology

1. Biology Copyright Pearson Prentice Hall

2. 12–1 DNA Copyright Pearson Prentice Hall

3. Griffith and Transformation Griffith and Transformation In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused pneumonia. He isolated two different strains of pneumonia bacteria from mice and grew them in his lab. Copyright Pearson Prentice Hall

4. Griffith and Transformation Griffith made two observations: (1) The disease-causing strain of bacteria grew into smooth colonies on culture plates. (2) The harmless strain grew into colonies with rough edges. Copyright Pearson Prentice Hall

5. Griffith and Transformation Griffith's Experiments Griffith set up four individual experiments. Experiment 1: Mice were injected with the disease-causing strain of bacteria. The mice developed pneumonia and died. Copyright Pearson Prentice Hall

6. 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 Copyright Pearson Prentice Hall

7. 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 Copyright Pearson Prentice Hall

8. Griffith and Transformation Heat-killed disease-causing bacteria (smooth colonies) Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died. Harmless bacteria (rough colonies) Live disease-causing bacteria(smooth colonies) Dies of pneumonia Copyright Pearson Prentice Hall

9. Griffith and Transformation Heat-killed disease-causing bacteria (smooth colonies) Griffith concluded that the heat-killed bacteria passed their disease-causing ability to the harmless strain. Harmless bacteria (rough colonies) Live disease-causing bacteria(smooth colonies) Dies of pneumonia Copyright Pearson Prentice Hall

10. Griffith and Transformation Transformation  Griffith called this process transformation because one strain of bacteria (the harmless strain) had changed permanently into another (the disease-causing strain). Griffith hypothesized that a factor must contain information that could change harmless bacteria into disease-causing ones. Copyright Pearson Prentice Hall

11. Avery and DNA Avery and DNA Oswald Avery repeated Griffith’s work to determine which molecule was most important for transformation. Avery and his colleagues made an extract from the heat-killed bacteria that they treated with enzymes. Copyright Pearson Prentice Hall

12. Avery and DNA The enzymes destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNA. Transformation still occurred. Copyright Pearson Prentice Hall

13. Avery and DNA Avery and other scientists repeated the experiment using enzymes that would break down DNA. When DNA was destroyed, transformation did not occur. Therefore, they concluded that DNA was the transforming factor. Copyright Pearson Prentice Hall

14. Avery and DNA Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next. Copyright Pearson Prentice Hall

15. The Hershey-Chase Experiment The Hershey-Chase Experiment Alfred Hershey and Martha Chase studied viruses—nonliving particles smaller than a cell that can infect living organisms. Copyright Pearson Prentice Hall

16. The Hershey-Chase Experiment Bacteriophages  A virus that infects bacteria is known as a bacteriophage. Bacteriophages are composed of a DNA or RNA core and a protein coat. Copyright Pearson Prentice Hall

17. The Hershey-Chase Experiment They grew viruses in cultures containing radioactive isotopes of phosphorus-32 (32P) and sulfur-35 (35S). Copyright Pearson Prentice Hall

18. The Hershey-Chase Experiment If 35S was found in the bacteria, it would mean that the viruses’ protein had been injected into the bacteria. Phage infects bacterium Bacteriophage with suffur-35 in protein coat No radioactivity inside bacterium Copyright Pearson Prentice Hall

19. The Hershey-Chase Experiment If 32P 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 Copyright Pearson Prentice Hall

20. The Hershey-Chase Experiment Nearly all the radioactivity in the bacteria was from phosphorus (32P). Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein. Copyright Pearson Prentice Hall

21. The Components and Structure of DNA The Components and Structure of DNA DNA is made up of nucleotides. A nucleotide is a monomer of nucleic acids made up of: • Deoxyribose – 5-carbon Sugar • Phosphate Group • Nitrogenous Base Copyright Pearson Prentice Hall

22. The Components and Structure of DNA There are four kinds of bases in in DNA: • adenine • guanine • cytosine • thymine Copyright Pearson Prentice Hall

23. The Components and Structure of DNA Chargaff's Rules Erwin Chargaff discovered that: • The percentages of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA. • The percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA. Copyright Pearson Prentice Hall

24. The Components and Structure of DNA X-Ray Evidence  Rosalind Franklin used X-ray diffraction to get information about the structure of DNA. She aimed an X-ray beam at concentrated DNA samples and recorded the scattering pattern of the X-rays on film. Copyright Pearson Prentice Hall

25. The Components and Structure of DNA The Double Helix  Using clues from Franklin’s pattern, James Watson and Francis Crick built a model that explained how DNA carried information and could be copied. Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other. Copyright Pearson Prentice Hall

26. The Components and Structure of DNA DNA Double Helix Copyright Pearson Prentice Hall

27. The Components and Structure of DNA Watson and Crick discovered that hydrogen bonds can form only between certain base pairs—adenine and thymine, and guanine and cytosine. This principle is called base pairing. Copyright Pearson Prentice Hall

28. 12–1 Copyright Pearson Prentice Hall

29. 12–1 Avery and other scientists discovered that • DNA is found in a protein coat. • DNA stores and transmits genetic information from one generation to the next. • transformation does not affect bacteria. • proteins transmit genetic information from one generation to the next. Copyright Pearson Prentice Hall

30. 12–1 The Hershey-Chase experiment was based on the fact that • DNA has both sulfur and phosphorus in its structure. • protein has both sulfur and phosphorus in its structure. • both DNA and protein have no phosphorus or sulfur in their structure. • DNA has only phosphorus, while protein has only sulfur in its structure. Copyright Pearson Prentice Hall

31. 12–1 DNA is a long molecule made of monomers called • nucleotides. • purines. • pyrimidines. • sugars. Copyright Pearson Prentice Hall

32. 12–1 Chargaff's rules state that the number of guanine nucleotides must equal the number of • cytosine nucleotides. • adenine nucleotides. • thymine nucleotides. • thymine plus adenine nucleotides. Copyright Pearson Prentice Hall

33. 12–1 In DNA, the following base pairs occur: • A with C, and G with T. • A with T, and C with G. • A with G, and C with T. • A with T, and C with T. Copyright Pearson Prentice Hall

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