Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 16 The Molecular Basis of Inheritance

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Griffith called the phenomenon transformation – Now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacteriophages Figure 16.3 Phage head Tail Tail fiber DNA Bacterial cell 100 nm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Section 12-1 Figure 12–4 Hershey-Chase Experiment

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Section 12-1 Figure 12–4 Hershey-Chase Experiment

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 16.7a, c C T A A T C G GC A C G A T A T AT T A C T A 0.34 nm 3.4 nm (a) Key features of DNA structure G 1 nm G (c) Space-filling model T

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings N H O CH 3 N N O N N N NH Sugar Adenine (A) Thymine (T) N N N N Sugar O H N H N H N O H H N Guanine (G) Cytosine (C) Figure 16.8 H

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Figure 12–7 Structure of DNA Section 12-1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings O –O–O O OH O –O–O O O H2CH2C O –O–O O O H2CH2C O –O–O O O O O O T A C G C A T O O O CH 2 O O–O– O O 5 end Hydrogen bond 3 end G P P P P O OH O–O– O O O P P O–O– O O O P O–O– O O O P (b) Partial chemical structure H2CH2C 5 end Figure 16.7b O

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Chromosome Structure of Eukaryotes Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure a–c Conservative model. The two parental strands reassociate after acting as templates for new strands, thus restoring the parental double helix. Semiconservative model. The two strands of the parental molecule separate, and each functions as a template for synthesis of a new, comple- mentary strand. Dispersive model. Each strand of both daughter mol- ecules contains a mixture of old and newly synthesized DNA. Parent cell First replication Second replication DNA replication is semiconservative (a) (b) (c)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In DNA replication – The parent molecule unwinds, and two new daughter strands are built based on base- pairing rules (a) The parent molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding with its specific partner, A with T and G with C. (b) The first step in replication is separation of the two DNA strands. (c) Each parental strand now serves as a template that determines the order of nucleotides along a new, complementary strand. (d) The nucleotides are connected to form the sugar-phosphate backbones of the new strands. Each “daughter” DNA molecule consists of one parental strand and one new strand. A C T A G A C T A G A C T A G A C T A G T G A T C T G A T C A C T A G A C T A G T G A T C T G A T C T G A T C T G A T C Figure 16.9 a–d

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 12–11 DNA Replication Section 12-2 Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand