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© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor,

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Presentation on theme: "© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor,"— Presentation transcript:

1 © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 10 Molecular Biology of the Gene

2 THE STRUCTURE OF THE GENETIC MATERIAL © 2012 Pearson Education, Inc.

3 Experiments showed that DNA is the genetic material Requirements for the genetic material: Must be able to code for unlimited amount of information Must be stable Yet able to change (everyone has a unique genetic sequence) Until the 1940s, the case for proteins serving as the genetic material was stronger than the case for DNA. –Proteins are made from 20 different amino acids. –DNA was known to be made from just four kinds of nucleotides. © 2012 Pearson Education, Inc.

4 Experiments showed that DNA is the genetic material Frederick Griffith discovered that a transforming factor could be transferred into a bacterial cell. Hershey and Chase experiment Only radio-labeled DNA entered bacteria cell © 2012 Pearson Education, Inc. Animation: Phage T2 Reproductive Cycle Animation: Hershey-Chase Experiment

5 LE 16-2 Living S cells (control) Living R cells (control) Heat-killed S cells (control) Mixture of heat-killed S cells and living R cells Mouse dies Living S cells are found in blood sample Mouse healthy Mouse dies RESULTS

6 LE 16-3 Bacterial cell Phage head Tail Tail fiber DNA 100 nm

7 Figure 10.1A Head Tail Tail fiber DNA

8 Phage Bacterium Batch 2: Radioactive DNA labeled in green DNA Radioactive protein Centrifuge Phage DNA Empty protein shell Pellet The radioactivity is in the liquid. Radioactive DNA Centrifuge Pellet The radioactivity is in the pellet Batch 1: Radioactive protein labeled in yellow Radioactive Sulfur used to label protein Radioactive Phosphorous used to label DNA

9 10.2 DNA and RNA are polymers of nucleotides DNA and RNA are nucleic acids. One of the two strands of DNA is a DNA polynucleotide, a nucleotide polymer (chain). A nucleotide is composed of a –nitrogenous base, –five-carbon sugar, and –phosphate group. The nucleotides are joined to one another by a COVALENT BOND between sugar-phosphate backbone. © 2012 Pearson Education, Inc. Animation: DNA and RNA Structure

10 Phosphate group Sugar (deoxyribose) DNA nucleotide Thymine (T) Cytosine (C) PyrimidinesPurines Adenine (A) Guanine (G) Nitrogenous base (can be A, G, C, or T)

11 RNA RNA (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. –RNA is a single, linear strand © 2012 Pearson Education, Inc. Phosphate group Sugar (ribose) Uracil (U) Nitrogenous base (can be A, G, C, or U)

12 Figure 10.2D Uracil Adenine Cytosine Guanine Ribose Phosphate

13 A A A A A A A C T T T T T T C C C C G G G G G C CG A T A DNA double helix T DNA nucleotide Covalent bond joining nucleotides A C T Two representations of a DNA polynucleotide G G G G C T Phosphate group Sugar (deoxyribose) DNA nucleotide Thymine (T) Nitrogenous base (can be A, G, C, or T) Sugar Nitrogenous base Phosphate group Sugar-phosphate backbone The nucleotides are joined to one another by a COVALENT BOND between sugar-phosphate backbone.

14 Sugar–phosphate backbone 5 end Nitrogenous bases Thymine (T) Adenine (A) Cytosine (C) DNA nucleotide Phosphate 3 end Guanine (G) Sugar (deoxyribose) The nucleotides are joined to one another by a COVALENT BOND between sugar- phosphate backbone.

15 Figure 10.3B

16 LE 16-6 Franklins X-ray diffraction photograph of DNA Rosalind Franklin

17 DNA is a double-stranded helix In 1953, James D. Watson and Francis Crick deduced the secondary structure of DNA, using –X-ray crystallography data of DNA from the work of Rosalind Franklin and Maurice Wilkins and –Chargaffs 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.

18 Chargaffs Rule: Equal proportion of A:T and G:C

19 Watson 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, forming two hydrogen bonds, and –G pairs with C, forming three hydrogen bonds SCIENTIFIC DISCOVERY: DNA is a double-stranded helix © 2012 Pearson Education, Inc. Animation: DNA Double Helix

20 Figure 10.3C Twist

21 5 end 3 end 5 end 3 end Space-filling modelPartial chemical structure Hydrogen bond Key features of DNA structure 0.34 nm 3.4 nm 1 nm Nucleotides in opposing strands are connected by HYDROGEN bonds Notice the two nucleotide strands run anti-parallel (opposite) of each other!

22 LE 16-8 Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Sugar


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