Chapter 16: The Molecular Basis of Inheritance PDF

Chapter 16 The Molecular Basis of Inheritance Learning Objectives Describe the structure of DNA and explain how it facilitates replication. Outline the process of DNA replication. Your answer should include the following terms: semiconservative replication, antiparallel, 5’ to 3’,...

Chapter 16 The Molecular Basis of Inheritance Learning Objectives Describe the structure of DNA and explain how it facilitates replication. Outline the process of DNA replication. Your answer should include the following terms: semiconservative replication, antiparallel, 5’ to 3’, leading strand, lagging strand, origin of replication, replication bubble, replication fork, + all DNA replication proteins listed in table 16.1 Figure 16.23 Exploring chromatin packing in a eukaryotic chromosome Evidence That Viral DNA Can Program Cells Experiment Batch 1: Radioactive sulfur (35S) in phage protein 1 Labeled phages 2 Agitation frees outside 3 Centrifuged cells infect cells. phage parts from form a pellet. cells. Radioactive 4 Radioactivity protein (phage protein) found in liquid Centrifuge Pellet Batch 2: Radioactive phosphorus (32P) in phage DNA Radioactive DNA Centrifuge Pellet 4 Radioactivity (phage DNA) found in pellet Figure 16.4 Additional Evidence That DNA Is the Genetic Material Sugar– 5′ end Nitrogenous phosphate bases backbone Thymine (T) Adenine (A) Cytosine (C) Phosphate Guanine (G) 3′ end Sugar DNA (deoxyribose) Nitrogenous nucleotide base Figure 16.5 (b) X-ray diffraction photograph of DNA Building a Structural Model of DNA: Scientific Inquiry 5′ C end C GG Hydrogen bond 3′ G C end G C T A 3.4 nm T A C G C G G C A T 1 nm C G T A C G G C C G A T A T 3′ A T end T A 0.34 nm 5′ (b) Partial chemical structure end (a) Key features of DNA structure a n ti p a Building a Structural Model of DNA: Scientific Inquiry Purine (A & G) + purine: too wide Pyrimidine (T & C) + pyrimidine: too narrow Purine + pyrimidine: width consistent with X-ray data Figure 16.UN02  First Parent cell Second replication replication (a) Conservative model (b) Semiconservative model (c) Dispersive model Figure 16.10 The Basic Principle: Base Pairing to a Template Strand A T A T A T A T C G C G C G C G T A T A T A T A A T A T A T A T G C G C G C G C (a) Parental (b) Separation of parental (c) Formation of new strands molecule strands into templates complementary to template strands Semiconservative model of replication predicts that when a double helix replicates, each daughter molecule will have one old strand (“conserved” from the parent molecule) and one newly made strand Figure 16.9-3 (a) Origin of replication in an E. coli cell (b) Origins of replication in a eukaryotic cell Origin of Origin of Parental (template) replication Eukaryotic chromosome replication strand Daughter (new) strand Parental (template) Double-stranded strand Replication DNA molecule Daughter (new) Bacterial fork strand chromosome Double- Replication stranded bubble Replication DNA molecule Bubble fork Two daughter DNA molecules Two daughter DNA molecules 0.25 µm 0.5 µm Figure 16.12 A large team of enzymes and other proteins carries out DNA replication. Primase Topoisomerase 3′ RNA 5′ 3′ prim 5′ er Replication 3′ fork 5′ Helicase Single-strand binding proteins Figure 16.13  New strand Template strand 5′ 3′ 5′ 3′ Sugar A T A T Phosphate Base C G C G DNA G C G C poly- OH merase 3′ A T A OH P P C 3′ C iPyro- phosphate Nucleotide 5′ 5′ 2P i Figure 16.14 Building a Structural Model of DNA: Scientific Inquiry 5′ C end C GG Hydrogen bond 3′ G C end G C T A 3.4 nm T A C G C G G C A T 1 nm C G T A C G G C C G A T A T 3′ A T end T A 0.34 nm 5′ (b) Partial chemical structure end (a) Key features of DNA structure a n ti p a  Overview Leading Leading strand Origin of replication Lagging strand Strand Primer Synthesis Leading strand Lagging strand Overall directions of 1 DNA pol III starts to replicatio Origin of replication n synthesize leading 3′ strand. 5′ RNA primer 5′ 3′ Sliding clamp 3′ DNA pol III Parental DNA 5′ 3′ 5′ 5′ 2 Continuous 3′ 3′ elongation in the 5′ to 3′ direction 5′ Figure 16.15 Lagging Strand Lagging Origin of replication Leading strand Lagging strand strand Synthesis 2 3′ 1 Primase makes 1 Leading strand RNA primer. Overall directions Origin of of replication 5′ replication 3′ Template 5′ 3′ 5′ strand 2 DNA pol III 3′ RNA primer makes Okazaki for fragment 1 fragment 1. 5′ 1 3′ 5′ 3′ 5′ 3 DNA pol III 3′ detaches. Okazaki 5′ fragment 1 1 3′ 5′ Figure 16.16b-3  Laggi RNA primer for fragment 2 ng 5′ Okaz 4 DNA pol III 3′ aki makes Okazaki Strand fragm fragment 2. ent 2 Synthe 2 1 3′ sis 5′ 5′ 3′ 5 DNA pol I replaces RNA with DNA. 2 1 3′ 5′ 6 DNA ligase 5′ forms bonds 3′ between DNA fragments. 2 1 3′ 5′ Overall direction of replication Figure 16.16c-3 Learn these! Table 16.1 Proofreading and Repairing DNA DNA polymerases proofread newly made DNA, replacing any incorrect nucleotides In mismatch repair of DNA, repair enzymes correct errors in base pairing DNA can be damaged by exposure to harmful chemical or physical agents such as cigarette smoke and X‐rays; it can also undergo spontaneous changes  Proofreading 5′ 3′ and Repairing 3′ 5′ Nuclease DNA In nucleotide excision repair, a nuclease cuts out 5′ 3′ and replaces damaged 3′ 5′ stretches of DNA DNA can be damaged by DNA polymerase exposure to harmful chemical or physical agents such as cigarette 5′ 3′ smoke and X‐rays; it can also undergo spontaneous changes 3′ 5′ DNA ligase 5′ 3′ 3′ 5′ © 2014 Pearson Education, Inc. Figure 16.19-3 Evolutionary Significance of Altered DNA Nucleotides Error rate after proofreading repair is low but not zero Sequence changes may become permanent and can be passed on to the next generation These changes (mutations) are a source of the genetic variation upon which natural selection operates  5′ Ends of parental Leading strand DNA strands Lagging strand 3′ Next-to-last Replicati Last fragment fragment ng the Lagging strand RNA primer 5′ Ends of 3′ DNA Parental strand Removal of primers and replacement with DNA Molecule where a 3′ end is available 5′ s 3′ Second round of replication 5′ New leading strand 3′ New lagging strand 5′ 3′ Further rounds © 2014 Pearson Education, Inc. of replication Figure 16.20 1 µm Shorter and shorter daughter