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 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

4. End Show 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. End Show 12–1 DNA Slide 5 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.

6. End Show 12–1 DNA Slide 6 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.

7. End Show 12–1 DNA Slide 7 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.

8. End Show 12–1 DNA Slide 8 of 37 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA Double Helix

9. End Show 12–1 DNA Slide 9 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.

10. End Show - or - Continue to: Click to Launch: Slide 10 of 37 Copyright Pearson Prentice Hall 12–1

11. End Show Slide 11 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.

12. End Show Slide 12 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.

13. End Show Slide 13 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.

14. END OF SECTION