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

2. 12–1 DNA Slide 2 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA What is the overall structure of the DNA molecule?

3. 12–1 DNA Slide 3 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 1.Five-carbon sugar called deoxyribose 2.Phosphate group 3.Nitrogenous base.

4. 12–1 DNA Slide 4 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

5. 12–1 DNA Slide 5 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA The backbone of a DNA chain (the sides of the ladder) is formed by sugar and phosphate groups of each nucleotide.

6. 12–1 DNA Slide 6 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.

7. 12–1 DNA Slide 7 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.

8. 12–1 DNA Slide 8 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.

9. 12–1 DNA Slide 9 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA Double Helix

10. 12–1 DNA Slide 10 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.

11. Slide 11 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.

12. Slide 12 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.

13. Slide 13 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.

14. Slide 14 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.

15. Slide 15 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.

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