Essentials of genetics / 6th ed.

TABLE OF CONTENTS
CHAPTER 1
Introduction to Genetics 1
1.1 From Mendel to DNA in Less Than a Century 2
1.2 Discovery of the Double Helix Launched the Era of Molecular Genetics 5
1.3 Genomics Grew Out of Recombinant DNA Technology 7
1.4 The Impact of Biotechnology Is Growing 8
1.5 Genetic Studies Rely on the Use of Model Organisms 11
1.6 We live in the ¿Age of Genetics¿ 14
GENETICS, TECHNOLOGY, AND SOCIETY 14
Chapter Summary 15
Key Terms 15
Problems and Discussion Questions 16
CHAPTER 2
Mitosis and Meiosis 17
2.1 Cell Structure Is Closely Tied to Genetic Function 18
2.2 Chromosomes Exist in Homologous Pairs in Diploid Organisms 20
2.3 Mitosis Partitions Chromosomes into Dividing Cells 22
2.4 Meiosis Reduces the Chromosome Number from Diploid to Haploid in Germ Cells and Spores 26
2.5 The Development of Gametes Varies during Spermatogenesis and Oogenesis 29
2.6 Meiosis Is Critical to the Successful Sexual Reproduction of All Diploid Organisms 31
2.7 Electron Microscopy Has Revealed the Cytological Nature of Mitotic and Meiotic Chromosomes 32
Chapter Summary 34
Key Terms 34
Insights and Solutions 35
Problems and Discussion Questions 36
CHAPTER 3
Mendelian Genetics 38
3.1 Mendel Used a Model Experimental Approach to Study Patterns of Inheritance 39
3.2 The Monohybrid Cross Reveals How One Trait Is Transmitted from Generation to Generation 39
3.3 Mendel¿s Dihybrid Cross Generated a Unique F2 Ratio 43
How Mendel¿s Peas Become Wrinkled: A Molecular Explanation 43
3.4 The Trihybrid Cross Demonstrates That Mendel¿s Principles Apply to Inheritance of Multiple Traits 46
3.5 Mendel¿s Work Was Rediscovered in the Early Twentieth Century 47
3.6 Independent Assortment Leads to Extensive Genetic Variation 49
3.7 Laws of Probability Help to Explain Genetic Events 49
3.8 Chi-Square Analysis Evaluates the Influence of Chance on Genetic Data 50
3.9 Pedigrees Reveal Patterns of Inheritance of Human Traits 52
GENETICS, TECHNOLOGY, AND SOCIETY
Tay-Sachs Disease: The Molecular Basis of a Recessive Disorder in Humans 55
Chapter Summary 55
Key Terms 56
Insights and Solutions 56
Problems and Discussion Questions 58
CHAPTER 4
Modification of Mendelian Ratios 61
4.1 Alleles Alter Phenotypes in Different Ways 62
4.2 Geneticists Use a Variety of Symbols for Alleles 63
4.3 Neither Allele Is Dominant in Incomplete, or Partial, Dominance 63
4.4 In Codominance, the Influence of Both Alleles in a Heterozygote Is Clearly Evident 64
4.5 Multiple Alleles of a Gene May Exist in a Population 64
4.6 Lethal Alleles Represent Essential Genes 65
4.7 Combinations of Two Gene Pairs with Two Modes of Inheritance Modify the 9:3:3:1 Ratio 67
4.8 Phenotypes Are Often Affected by More than One Gene 67
4.9 Complementation Analysis Can Determine If Two Mutations Causing a Similar Phenotype Are Alleles of the Same Gene 72
4.10 X-Linkage Describes Genes on the X Chromosome 73
4.11 In Sex-Limited and Sex-Influenced Inheritance, an Individual¿s Sex Influences the Phenotype 76
4.12 Genetic Background and the Environment Affect Phenotypic Expression 77
4.13 Extranuclear Inheritance Modifies Mendelian Patterns 80
GENETICS, TECHNOLOGY, AND SOCIETY
Mitochondrial DNA and the Mystery of the Romanovs 85
Chapter Summary 86
Key Terms 87
Insights and Solutions 87
Problems and Discussion Questions 89
CHAPTER 5
Sex Determination and Sex Chromosomes 94
5.1 Life Cycles Depend on Sexual Differentiation 95
5.2 X and Y Chromosomes Were First Linked to Sex Determination Early in the Twentieth Century 98
5.3 The Y Chromosome Determines Maleness in Humans 99
5.4 The Ratio of Males to Females in Humans Is Not 1.0 104
5.5 Dosage Compensation Prevents Excessive Expression of X-Linked Genes in Humans and Other Mammals 104
5.6 The Ratio of X Chromosomes to Sets of Autosomes Determines Sex in Drosophila 107
5.7 Temperature Variation Controls Sex Determination in Reptiles 109
GENETICS, TECHNOLOGY, AND SOCIETY
A Question of Gender: Sex Selection in Humans 110
Chapter Summary 111
Key Terms 112
Insights and Solutions 112
Problems and Discussion Questions 112
CHAPTER 6
Chromosome Mutations: Variation in Number and Arrangement 114
6.1 Specific Terminology Describes Variations in Chromosome Number 115
6.2 Variation in the Number of Chromosomes Results from Nondisjunction 115
6.3 Monosomy, the Loss of a Single Chromosome, May Have Severe Phenotypic Effects 116
6.4 Trisomy Involves the Addition of a Chromosome to a Diploid Genome 117
6.5 Polyploidy, in Which More Than Two Haploid Sets of Chromosomes Are Present, Is Prevalent in Plants 120
6.6 Variation Occurs in the Composition and Arrangement of Chromosomes 122
6.7 A Deletion Is a Missing Region of a Chromosome 123
6.8 A Duplication Is a Repeated Segment of a Chromosome 124
6.9 Inversions Rearrange the Linear Gene Sequence 126
6.10 Translocations Alter the Location of Chromosomal Segments in the Genome 128
6.11 Fragile Sites in Humans Are Susceptible to Chromosome Breakage 129
GENETICS, TECHNOLOGY, AND SOCIETY
The Link between Fragile Sites and Cancer 131
Chapter Summary 132
Key Terms 132
Insights and Solutions 133
Problems and Discussion Questions 133
CHAPTER 7
Linkage and Chromosome Mapping in Eukaryotes 136
7.1 Genes Linked on the Same Chromosome Segregate Together 137
7.2 Crossing Over Serves as the Basis of Determining the Distance Between Genes During Mapping 140
7.3 Determining the Gene Sequence During Mapping Relies on the Analysis of Multiple Crossovers 143
7.4 As the Distance Between Two Genes Increases, Mapping Estimates Become More Inaccurate 150
7.5 Drosophila Genes Have Been Extensively
Mapped 151
7.6 Lod Score Analysis and Somatic Cell Hybridization Were Historically Important in Creating Human Chromosome Maps 152
7.7 Linkage and Mapping Studies Can Be Performed in Haploid Organisms 154
7.8 Other Aspects of Genetic Exchange 154
7.9 Did Mendel Encounter Linkage? 157
Why Didn¿t Gregor Mendel Find Linkage? 157
Chapter Summary 158
Key Terms 158
Insights and Solutions 158
Problems and Discussion Questions 160
CHAPTER 8
Genetic Analysis and Mapping in Bacteria and Bacteriophages 164
8.1 Bacteria Mutate Spontaneously and Grow at an Exponential Rate 165
8.2 Conjugation Is One Means of Genetic Recombination in Bacteria 166
8.3 Rec Proteins Are Essential to Bacterial Recombination 172
8.4 F Factors Are Plasmids 174
8.5 Transformation Is Another Process Leading to Genetic Recombination in Bacteria 174
8.6 Bacteriophages Are Bacterial Viruses 176
8.7 Transduction Is Virus-Mediated Bacterial DNA Transfer 179
8.8 Bacteriophages Undergo Intergenic Recombination 181
GENETICS, TECHNOLOGY, AND SOCIETY
Bacterial Genes and Disease: From Gene Expression to Edible Vaccines 183
Chapter Summary 184
Key Terms 184
Insights and Solutions 185
Problems and Discussion Questions 186
CHAPTER 9
DNA Structure and Analysis 188
9.1 The Genetic Material Must Exhibit Four Characteristics 189
9.2 Until 1944, Observations Favored Protein as the Genetic Material 190
9.3 Evidence Favoring DNA as the Genetic Material Was First Obtained During the Study of Bacteria and Bacteriophages 190
9.4 Indirect and Direct Evidence Supports the Concept that DNA Is the Genetic Material in Eukaryotes 195
9.5 RNA Serves as the Genetic Material in Some Viruses 196
9.6 The Structure of DNA Holds the Key to Understanding Its Function 197
Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid 202
9.7 Alternative Forms of DNA Exist 203
9.8 The Structure of RNA Is Chemically Similar to DNA, but Single-Stranded 204
9.9 Many Analytical Techniques Have Been Useful During the Investigation of DNA and RNA 205
9.10 Nucleic Acids Can Be Separated Using Electrophoresis 207
Chapter Summary 208
GENETICS, TECHNOLOGY, AND SOCIETY
The Twists and Turns of the Helical Revolution 209
Key Terms 210
Insights and Solutions 210
Problems and Discussion Questions 211
CHAPTER 10
DNA Replication and Synthesis 213
10.1 DNA Is Reproduced by Semiconservative Replication 214
10.2 DNA Synthesis in Bacteria Involves Five Polymerases, as well as Other Enzymes 218
10.3 Many Complex Issues Must Be Resolved During DNA Replication 221
10.4 A Coherent Model Summarizes DNA Replication 224
10.5 Replication Is Controlled by a Variety of Genes 224
10.6 Eukaryotic DNA Synthesis Is Similar to Synthesis in Prokaryotes but More Complex 225
10.7 The Ends of Linear Chromosomes Are Problematic During Replication 227
10.8 DNA Recombination, Like DNA Replication, Is Directed by Specific Enzymes 228
GENETICS, TECHNOLOGY, AND SOCIETY
Telomerase: The Key to Immortality? 231
Chapter Summary 232
Key Terms 232
Insights and Solutions 233
Problems and Discussion Questions 233
CHAPTER 11
Chromosome Structure and DNA Sequence Organization 235
11.1 Viral and Bacterial Chromosomes Are Relatively Simple DNA Molecules 236
11.2 Mitochondria and Chloroplasts Contain DNA Similar to Bacteria and Viruses 237
11.3 Specialized Chromosomes Reveal Variations in the Organization of DNA 240
11.4 DNA Is Organized into Chromatin in Eukaryotes 242
11.5 Eukaryotic Genomes Demonstrate Complex Sequence Organization Characterized by Repetitive DNA 246
11.6 The Vast Majority of a Eukaryotic Genome Does Not Encode Functional Genes 249
Chapter Summary 249
Key Terms 250
Insights and Solutions 250
Problems and Discussion Questions 251
CHAPTER 12
The Genetic Code and Transcription 253
12.1 The Genetic Code Exhibits a Number of Characteristics 254
12.2 Early Studies Established the Basic Operational Patterns of the Code 255
12.3 Studies by Nirenberg, Matthaei, and Others Deciphered the Code 255
12.4 The Coding Dictionary Reveals the Function of the 64 Triplets 259
12.5 The Genetic Code Has Been Confirmed in Studies of Bacteriophage MS2 261
12.6 The Genetic Code Is Nearly Universal 261
12.7 Different Initiation Points Create Overlapping Genes 262
12.8 Transcription Synthesizes RNA on a DNA Template 262
12.9 RNA Polymerase Directs RNA Synthesis 263
12.10 Transcription in Eukaryotes Differs from Prokaryotic Transcription in Several Ways 265
12.11 The Coding Regions of Eukaryotic Genes Are Interrupted by Intervening Sequences Called Introns 267
12.12 RNA Editing Modifies the Final Transcript 270
12.13 Transcription Has Been Visualized by Electron Microscopy 270
Chapter Summary 271
GENETICS, TECHNOLOGY, AND SOCIETY
Antisense Oligonucleotides: Attacking the Messenger 272
Key Terms 273
Insights and Solutions 273
Problems and Discussion Questions 274
CHAPTER 13
Translation and Proteins 277
13.1 Translation of mRNA Depends on Ribosomes and Transfer RNAs 278
13.2 Translation of mRNA Can Be Divided into Three Steps 282
13.3 Crystallographic Analysis Has Revealed Many Details about the Functional Prokaryotic Ribosome 284
13.4 Translation Is More Complex in Eukaryotes 285
13.5 The Initial Insight that Proteins Are Important in Heredity Was Provided by the Study of Inborn Errors of Metabolism 286
13.6 Studies of Neurospora Led to the One-Gene:One-Enzyme Hypothesis 287
13.7 Studies of Human Hemoglobin Established that One Gene Encodes One Polypeptide 289
13.8 Protein Structure Is the Basis of Biological Diversity 291
13.9 Posttranslational Modification Alters the Final Protein Product 294
13.10 Protein Function Is Directly Related to the Structure of the Molecule 295
13.11 Proteins Consist of Functional Domains 296
GENETICS, TECHNOLOGY, AND SOCIETY
Mad Cow Disease: The Prion Story 297
Chapter Summary 298
Key Terms 299
Insights and Solutions 300
Problems and Discussion Questions 300
CHAPTER 14
Gene Mutation, DNA Repair, and Transposition 303
14.1 Mutations Are Classified in Various Ways 304
14.2 The Spontaneous Mutation Rate Varies Greatly among Organisms 306
14.3 Spontaneous Mutations Arise from Replication Errors and Base Modifications 306
14.4 Induced Mutations Arise from DNA Damage Caused by Chemicals and Radiation 308
14.5 Genomics and Gene Sequencing Have Enhanced Our Understanding of Mutations in Humans 311
14.6 The Ames Test Is Used to Assess the Mutagenicity of Compounds 312
14.7 Organisms Use DNA Repair Systems to Counteract Mutations 313
14.8 Transposable Elements Move within the Genome and May Disrupt Genetic Function 317
14.9 Geneticists Use Mutations to Identify Genes and Study Gene Function 320
GENETICS, TECHNOLOGY, AND SOCIETY
In the Shadow of Chernobyl 324
Chapter Summary 325
Key Terms 325
Insights and Solutions 326
Problems and Discussion Questions 327
CHAPTER 15
Regulation of Gene Expression 329
15.1 Prokaryotes Regulate Gene Expression in Response to Environmental Conditions 330
15.2 Lactose Metabolism in E. coli Is Regulated by an Inducible System 331
15.3 The Catabolite-Activating Protein (CAP) Exerts Positive Control over the lac Operon 335
15.4 The Tryptophan (trp) Operon in E. coli Is a Repressible Gene System 336
15.5 Attenuation Is a Critical Process during the Regulation of the trp Operon in E. coli 338
15.6 Eukaryotic Gene Regulation Differs from That in Prokaryotes 338
15.7 Eukaryotic Gene Expression Is Influenced by Chromosome Organization and Chromatin Modifications 340
15.8 Eukaryotic Transcription Is Regulated at Specific Cis-Acting Sites 342
15.9 Eukaryotic Transcription is Regulated by Transcription Factors that Bind to Cis-Acting Sites 344
15.10 Eukaryotic Transcription Factors Regulate Transcription Through Interactions with Basal Transcription Factors 346
15.11 Alternative Splicing and mRNA Stability Can Regulate Eukaryotic Gene Expression 347
15.12 RNA Silencing Controls Gene Expression in Several Ways 349
GENETICS, TECHNOLOGY, AND SOCIETY
Gene Regulation and Human Genetic Disordersr 351
Chapter Summary 352
Key Terms 352
Insights and Solutions 353
Problems and Discussion Questions 354
CHAPTER 16
Cell-Cycle Regulation and Cancer 357
16.1 Cancer Is a Genetic Disease at the Level of Somatic Cells 358
16.2 Cancer Cells Contain Genetic Defects Affecting Genomic Stability and DNA Repair 360
16.3 Cancer Cells Contain Genetic Defects Affecting Cell-Cycle Regulation 361
16.4 Many Cancer-Causing Genes Disrupt Control of the Cell Cycle 364
16.5 Cancer Is a Genetic Disorder Affecting Cell¿Cell Contact 367
16.6 Predisposition to Some Cancers Can Be Inherited 367
16.7 Viruses Contribute to Cancer in Both Humans and Animals 369
16.8 Environmental Agents Contribute to Human Cancers 370
GENETICS, TECHNOLOGY, AND SOCIETY
Breast Cancer: The Double-Edged Sword of Genetic Testing 371
Chapter Summary 372
Key Terms 372
Insights and Solutions 373
Problems and Discussion Questions 374
CHAPTER 17
Recombinant DNA Technology 376
17.1 An Overview of Recombinant DNA Technology 377
17.2 Recombinant DNA Molecules Are Constructed from Several Components 377
17.3 Cloning in Host Cells 381
17.4 The Polymerase Chain Reaction Copies DNA Without Host Cells 382
17.5 Recombinant Libraries Are Collections of Cloned Sequences 384
17.6 Specific Clones Can Be Recovered from a Library 385
17.7 Cloned Sequences Can Be Analyzed in Several Ways 387
17.8 DNA Sequencing: The Ultimate Characterization of a Clone 390
GENETICS, TECHNOLOGY, AND SOCIETY
Beyond Dolly: The Cloning of Humans 393
Chapter Summary 394
Key Terms 394
Insights and Solutions 395
Problems and Discussion Questions 395
CHAPTER 18
Genomics and Proteomics 399
18.1 Structural Genomics uses DNA Sequencing to Study Genomes 401
18.2 Annotation is used to find Genes in DNA Sequence Data 402
18.3 Functional Genomics Classifies Genes and Identifies Their Functions 403
18.4 Prokaryotic Genomes Have Some Unexpected Features 405
18.5 Eukaryotic Genomes Have Several Organizational Patterns 407
18.6 Mapping the Human Genome was coordinated by the Human Genome Project 409
18.7 Comparative Genomics Is a Versatile Tool 411
18.8 Comparative Genomics: Evolution and Function in Multigene Families 413
18.9 Proteomics Identifies and Analyzes the Proteins in a Cell 417
GENETICS, TECHNOLOGY, AND SOCIETY
Beyond Dolly: The Cloning of Humans 420
Chapter Summary 421
Key Terms 421
Insights and Solutions 421
Problems and Discussion Questions 422
CHAPTER 19
Applications and Ethics of Genetic Engineering 425
19.1 Genetic Engineering Has Revolutionized Agriculture 426
19.2 Genetically Engineered Organisms Synthesize a Wide Range of Biological and Pharmaceutical Products 428
19.3 Genetic Engineering and Genomics Are Transforming Medical Diagnosis 431
19.4 Genetic Engineering and Genomics Promise New and Targeted Medical Therapies 437
19.5 DNA Profiles Help Identify Individuals 440
19.6 Genetic Engineering and Genomics Create Ethical, Social and Legal Questions 442
GENETICS, TECHNOLOGY, AND SOCIETY
Gene Therapy¿Two Steps Forward or Two Steps Back? 444
Chapter Summary 445
Key Terms 445
Insights and Solutions 445
Problems and Discussion Questions 446
CHAPTER 20
Developmental Genetics 449
20.1 The Study of Evolutionary Conservation of Developmental Mechanisms Using Model Organisms 450
20.2 Specification of the Body Axis using Genetic Analysis of Embryonic Development in Drosophila 451
20.3 Zygotic Genes Program Segment Formation 453
20.4 Homeotic Genes Specify Parts of the Adult Body 456
20.5 Cascades of Gene Action Control Differentiation 458
20.6 Plants Have Evolved Developmental Systems That Parallel Those of Animals 459
20.7 The Study of Cell¿Cell Interactions in Development Using C. elegans as a Model Organism 461
GENETICS, TECHNOLOGY, AND SOCIETY
Stem Cell Wars 465
Chapter Summary 466
Key Terms 466
Insights and Solutions 467
Problems and Discussion Questions 468
CHAPTER 21
Quantitative Genetics 470
21.1 Not All Polygenic Traits Show Continuous Variation 471
21.2 Quantitative Traits Can Be Explained in Mendelian Terms 472
21.3 The Study of Polygenic Traits Relies on Statistical Analysis 475
21.4 Heritability Estimates the Genetic Contribution to Phenotypic Variability 477
21.5 Twin Studies Allow an Estimation of Heritability in Humans 481
21.6 Quantitative Trait Loci Can Be Mapped 481
Chapter Summary 482
GENETICS, TECHNOLOGY, AND SOCIETY
The Green Revolution Revisited 483
Key Terms 484
Insights and Solutions 484
Problems and Discussion Questions 485
CHAPTER 22
Population Genetics 489
22.1 Allele Frequencies in Population Gene Pools Vary in Space and Time 490
22.2 The Hardy-Weinberg Law Describes the Relationship between Allele Frequencies and Genotype Frequencies in an Ideal Population 490
22.3 The Hardy-Weinberg Law Can Be Applied to Human Populations 492
22.4 The Hardy-Weinberg Law Can Be Used for Multiple Alleles and Estimating Heterozygote Frequencies 495
22.5 Natural Selection Is a Major Force Driving Allele Frequency Change 497
22.6 Mutation Creates New Alleles in a Gene Pool 502
22.7 Migration and Gene Flow Can Alter Allele Frequencies 503
22.8 Genetic Drift Causes Random Changes in Allele Frequency in Small Populations 504
22.9 Nonrandom Mating Changes Genotype Frequency but Not Allele Frequency 506
Chapter Summary 509
GENETICS, TECHNOLOGY, AND SOCIETY
Tracking Our Genetic Footprints out of Africa 510
Key Terms 511
Insights and Solutions 511
Problems and Discussion Questions 512
CHAPTER 23
Evolutionary Genetics 514
23.1 Speciation Can Occur by Transformation or by Splitting Gene Pools 515
23.2 Genetic Variation Is Present in Most Populations and Species 516
23.3 How Can We Explain High Levels of Genetic Variation? 518
23.4 The Genetic Structure of Populations Changes across Space and Time 518
23.5 Defining A Species Is a Challenge for Evolutionary Biology 521
23.6 Reduced Gene Flow, Selection, and Genetic Drift Can Lead to Speciation 521
23.7 Genetic Differences can be Used to Reconstruct Evolutionary History 526
23.8 Reconstructing Evolutionary History Allows Us to Answer Many Questions 530
Chapter Summary 532
GENETICS, TECHNOLOGY, AND SOCIETY
What Can We Learn from the Failure of the Eugenics
Movement? 533
Key Terms 534
Insights and Solutions 534
Problems and Discussion Questions 535
CHAPTER 24
Conservation Genetics 537
24.1 Genetic Diversity Is at the Heart of Conservation Genetics 539
24.2 Population Size Has a Major Impact on Species Survival 541
24.3 Genetic Effects Are More Pronounced in Small, Isolated Populations 543
24.4 Genetic Erosion Diminishes Genetic Diversity 545
24.5 Conservation of Genetic Diversity Is Essential to Species Survival 546
Chapter Summary 549
GENETICS, TECHNOLOGY, AND SOCIETY
Gene Pools and Endangered Species: The Plight of the Florida Panther 550
Key Terms 551
Insights and Solutions 551
Problems and Discussion Questions 552
APPENDIX A ANSWERS TO SELECTED PROBLEMS A¿1
APPENDIX B SELECTED READING A¿1
GLOSSARY G¿1
INDEX I¿1