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End Show Slide 1 of 37 Copyright Pearson Prentice Hall Biology.

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Presentation on theme: "End Show Slide 1 of 37 Copyright Pearson Prentice Hall Biology."— Presentation transcript:

1 End Show Slide 1 of 37 Copyright Pearson Prentice Hall Biology

2 End Show Slide 2 of 37 Copyright Pearson Prentice Hall 12–1 DNA

3 End Show 12–1 DNA Slide 3 of 37 Copyright Pearson Prentice Hall 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.

4 End Show 12–1 DNA Slide 4 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Alfred Hershey and Martha Chase studied viruses—nonliving particles smaller than a cell that can infect living organisms.

5 End Show 12–1 DNA Slide 5 of 37 Copyright Pearson Prentice Hall 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.

6 End Show 12–1 DNA Slide 6 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment When a bacteriophage enters a bacterium, the virus attaches to the surface of the cell and injects its genetic information into it. The viral genes produce many new bacteriophages, which eventually destroy the bacterium. When the cell splits open, hundreds of new viruses burst out.

7 End Show 12–1 DNA Slide 7 of 37 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein.

8 End Show Slide 8 of 37 What is the overall structure of the DNA molecule? Copyright Pearson Prentice Hall

9 End Show 12–1 DNA Slide 9 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA is made up of nucleotides. A nucleotide is a monomer of nucleic acids made up of 3 parts 1. five-carbon sugar called deoxyribose 2. a phosphate group 3. and a nitrogenous base.

10 End Show 12–1 DNA Slide 10 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

11 End Show 12–1 DNA Slide 11 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA The backbone of a DNA chain is formed by sugar and phosphate groups of each nucleotide. The nucleotides can be joined together in any order.

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

13 End Show 12–1 DNA Slide 13 of 37 Copyright Pearson Prentice Hall 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.

14 End Show 12–1 DNA Slide 14 of 37 Copyright Pearson Prentice Hall 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.

15 End Show 12–1 DNA Slide 15 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA Double Helix

16 End Show 12–1 DNA Slide 16 of 37 Copyright Pearson Prentice Hall 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. Quiz Tomorrow! Study! HW: WB 12-1 #17-28 Due Tomorrow!

17 End Show - or - Continue to: Click to Launch: Slide 17 of 37 Copyright Pearson Prentice Hall 12–1

18 End Show Slide 18 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.

19 End Show Slide 19 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.

20 End Show Slide 20 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.

21 End Show Slide 21 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.

22 End Show Slide 22 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.

23 END OF SECTION


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