1 Chapter 10 sections 1, 2,3 Student 2015

2 10.1 SCIENTIFIC DISCOVERY: Experiments showed that DNA is the genetic materialUntil the 1940s, the case for proteins serving as the genetic material was stronger than the case for DNA. © 2012 Pearson Education, Inc. 2

3 DNA is the Genetic Material Fredrick Griffith Experiment 1928:The Transforming Factor

4 Figure 10.1A Head DNA Tail Tail fiber Figure 10.1A Phage T2 4

5 DNA is the Genetic Material Hershey and Chase Experiment 1952

6 DNA is the Genetic Material Hershey and Chase Experiment 1952What convinced Hershey and Chase that DNA was the genetic material? © 2012 Pearson Education, Inc. 6

7 10.2 DNA and RNA are polymers of nucleotidesAt the time of Hershey and Chase much was known about the chemical make up of DNA however much was not understood. Specific arrangement of atoms How it stored genetic information copied it Passed genetic information from generation to generation

8 10.2 DNA and RNA are polymers of nucleotidesDNA and RNA are nucleic acids. Polymers A nucleotide (monomer)is composed of a nitrogenous base, five-carbon sugar, and phosphate group. © 2012 Pearson Education, Inc. 8

9 Thymine (T) Phosphate groupFigure 10.2A_3 Nitrogenous base (can be A, G, C, or T) Thymine (T) Phosphate group Figure 10.2A_3 The structure of a DNA polynucleotide (part 3) Sugar (deoxyribose) DNA nucleotide 9

10 DNA nitrogenous bases have a double or single ringThymine (T) Cytosine (C) Adenine (A) Guanine (G) Pyrimidines Purines Figure 10.2B The nitrogenous bases of DNA 10

11 The nucleotides are joined to one another by a sugar-phosphate backbone.

12 Sugar-phosphate backboneFigure 10.2A A T C G T A Sugar-phosphate backbone C G Phosphate group A T G C A G A Nitrogenous base Nitrogenous base (can be A, G, C, or T) Covalent bond joining nucleotides A T G C Sugar T A T A C C C C C G T A DNA nucleotide Thymine (T) A DNA double helix T T T Phosphate group Figure 10.2A The structure of a DNA polynucleotide G G Sugar (deoxyribose) DNA nucleotide G G Two representations of a DNA polynucleotide 12

13 10.2 DNA and RNA are Polymers of NucleotidesRNA (ribonucleic acid) is unlike DNA in that it uses the sugar ribose (instead of deoxyribose in DNA) and RNA has the nitrogenous base uracil (U) instead of thymine. Single strand © 2012 Pearson Education, Inc. 13

14 10.3 SCIENTIFIC DISCOVERY: DNA is a double-stranded helixIn 1952, the race was on to describe the structure of DNA and explain how the structure and properties of DNA can account for its role in heredity. © 2012 Pearson Education, Inc. 14

15 10.3 SCIENTIFIC DISCOVERY: DNA is a double-stranded helixIn 1953, James D. Watson and Francis Crick deduced the structure of DNA, using Chargaff’s observation that in DNA, the amount of adenine was equal to the amount of thymine and the amount of guanine was equal to that of cytosine. © 2012 Pearson Education, Inc. 15

16 10.3 SCIENTIFIC DISCOVERY: DNA is a double-stranded helixX-ray crystallography data of DNA from the work of Rosalind Franklin and Maurice Wilkins

17 10.3 SCIENTIFIC DISCOVERY: DNA is a double-stranded helixWatson and Crick reported that DNA consisted of two polynucleotide strands wrapped into a double helix. The sugar-phosphate backbone is on the outside. The nitrogenous bases are perpendicular to the backbone in the interior. Specific pairs of bases give the helix a uniform shape. A pairs with T, (complementary) 2 hydrogen bonds G pairs with C, (complementary) 3 hydrogen bonds Strands run antiparallel © 2012 Pearson Education, Inc. 17

18 Partial chemical structureFigure 10.3D Hydrogen bond Base pair Figure 10.3D Three representations of DNA Ribbon model Partial chemical structure Computer model 18

19 Animation: DNA Double HelixAnimation: DNA Double Helix Right click on animation / Click play © 2012 Pearson Education, Inc. 19