Introduction to Genetics Genetics Is Important to Us Individually, to Society, and to the Study of Biology Humans Have Been Using Genetics for Thousands of Years A Few Fundamental Concepts Are Important for the Start of Our Journey into Genetics Chromosomes and Cellular Reproduction Prokaryotic and Eukaryotic Cells Differ in a Number of Genetic Characteristics Cell Reproduction Requires the Copying of the Genetic Material, Separation of the Copies, and Cell Division Sexual Reproduction Produces Genetic Variation Through the Process of Meiosis Basic Principles of Heredity Gregor Mendel Discovered the Basic Principles of Heredity Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dihybrid Crosses Reveal the Principle of Independent Assortment Observed Ratios of Progeny May Deviate from Expected Ratios by Chance Sex Determination and Sex-Linked Characteristics Sex Is Determined by a Number of Different Mechanisms Sex-linked Characteristics Are Determined by Genes on the Sex Chromosomes Dosage Compensation Equalizes the Amount of Protein Produced by X-Linked Genes in Males and Females Extensions and Modifications of Basic Principles Additional Factors at a Single Locus Can Affect the Results of Genetic Crosses Gene Interaction Takes Place When Genes at Multiple Loci Determine a Single Phenotype Sex Influences the Inheritance and Expression of Genes in a Variety of Ways Anticipation Is the Stronger or Earlier Expression of Traits in Succeeding Generations The Expression of a Genotype May Be Affected by Environmental Effects Pedigree Analysis, Applications, and Genetic Testing The Study of Genetics in Humans Is Constrained by Special Features of Human Biology and Culture Geneticists Often Use Pedigrees to Study the Inheritance of Characteristics in Humans Studying Twins and Adoptions Can Help Assess the Importance of Genes and Environment Genetic Counseling and Genetic Testing Provide Information to Those Concerned about Genetic Diseases and Traits Comparison of Human and Chimpanzee Genomes Is Helping to Reveal Genes That Make Humans Unique Quantitative Genetics Quantitative Characteristics Vary Continuously and Many Are Influenced by Alleles at Multiple Loci Statistical Methods Are Required for Analyzing Quantitative Characteristics Heritability Is Used to Estimate the Proportion of Variation in a Trait That Is Genetic Genetically Variable Traits Change in Response to Selection Linkage, Recombination, and Eukaryotic Gene Mapping Linked Genes Do Not Assort Independently Linked Genes Segregate Together and Crossing Over Produces Recombination Between Them A Three-Point Testcross Can Be Used to Map Three Linked Genes Physical-Mapping Methods Are Used to Determine the Physical Positions of Genes on Particular Chromosomes Recombination Rates Exhibit Extensive Variation Bacterial and Viral Genetic Systems Genetic Analysis of Bacteria Requires Special Methods Bacteria Exchange Genes Through Conjugation, Transformation, and Transduction Viruses Are Simple Replicating Systems Amenable to Genetic Analysis Chromosome Variation Chromosome Mutations Include Rearrangements, Aneuploids, and Polyploids Chromosome Rearrangements Alter Chromosome Structure Aneuploidy Is an Increase or Decrease in the Number of Individual Chromosomes Polyploidy Is the Presence of More Than Two Sets of Chromosomes Chromosome Variation Plays an Important Role in Evolution DNA: The Chemical Nature of the Gene Genetic Material Possesses Several Key Characteristics All Genetic Information Is Encoded in the Structure of DNA or RNA DNA Consists of Two Complementary and Antiparallel Nucleotide Strands That Form a Double Helix Special Structures Can Form in DNA and RNA Chromosome Structure and Transposable Elements Large Amounts of DNA Are Packed into a Cell Eukaryotic Chromosomes Possess Centromeres and Telomeres Eukaryotic DNA Contains Several Classes of Sequence Variation Transposable Elements Are DNA Sequences Capable of Moving Different Types of Transposable Elements Have Characteristic Structures Transposable Elements Have Played an Important Role in Genome Evolution DNA Replication and Recombination Genetic Information Must Be Accurately Copied Every Time a Cell Divides All DNA Replication Takes Place in a Semiconservative Manner Bacterial Replication Requires a Large Number of Enzymes and Proteins Eukaryotic DNA Replication Is Similar to Bacterial Replication but Differs in Several Aspects Recombination Takes Place Through the Breakage, Alignment, and Repair of DNA Strands Transcription RNA, Consisting of a Single Strand of Ribonucleotides, Participates in a Variety of Cellular Functions Transcription Is the Synthesis of an RNA Molecule from a DNA Template The Process of Bacterial Transcription Consists of Initiation, Elongation, and Termination Eukaryotic Transcription Is Similar to Bacterial Transcription but Has Some Important Differences Transcription in Archaea Is More Similar to Transcription in Eukaryotes Than to Transcription in Eubacteria RNA Molecules and RNA Processing Many Genes Have Complex Structures Messenger RNAs, Which Encode the Amino Acid Sequences of Proteins, Are Modified after Transcription in Eukaryotes Transfer RNAs, Which Attach to Amino Acids, Are Modified after Transcription in Bacterial and Eukaryotic Cells Ribosomal RNA, a Component of the Ribosome, Also Is Processed after Transcription Small RNA Molecules Participate in a Variety of Functions The Genetic Code and Translation Many Genes Encode Proteins The Genetic Code Determines How the Nucleotide Sequence Specifies the Amino Acid Sequence of a Protein Amino Acids Are Assembled into a Protein Through the Mechanism of Translation Additional Properties of RNA and Ribosomes Affect Protein Synthesis Control of Gene Expression in Prokaryotes The Regulation of Gene Expression Is Critical for All Organisms Operons Control Transcription in Bacterial Cells Some Operons Regulate Transcription Through Attenuation, the Premature Termination of Transcription RNA Molecules Control the Expression of Some Bacterial Genes Control of Gene Expression in Eukaryotes Eukaryotic Cells and Bacteria Have Many Features of Gene Regulation in Common, but They Differ in Several Important Ways Changes in Chromatin Structure Affect the Expression of Genes Epigenetic Effects Often Result from Alterations in Chromatin Structure The Initiation of Transcription Is Regulated by Transcription Factors and Transcriptional Regulator Proteins Some Genes Are Regulated by RNA Processing and Degradation RNA Interference Is an Important Mechanism of Gene Regulation Some Genes Are Regulated by Processes That Affect Translation or by Modifications of Proteins Gene Mutations and DNA Repair Mutations Are Inherited Alterations in the DNA Sequence Mutations Are Potentially Caused by a Number of Different Natural and Unnatural Factors Mutations Are the Focus of Intense Study by Geneticists A Number of Pathways Repair Changes in DNA Molecular Genetic Analysis and Biotechnology Techniques of Molecular Genetics Have Revolutionized Biology Molecular Techniques Are Used to Isolate, Recombine, and Amplify Genes Molecular Techniques Can Be Used to Find Genes of Interest DNA Sequences Can Be Determined and Analyzed Molecular Techniques Are Increasingly Used to Analyze Gene Function Biotechnology Harnesses the Power of Molecular Genetics Genomics and Proteomics Structural Genomics Determines the DNA Sequences of Entire Genomes Functional Genomics Determines the Function of Genes by Using Genomic-Based Approaches Comparative Genomics Studies How Genomes Evolve Proteomics Analyzes the Complete Set of Proteins Found in a Cell Organelle DNA Mitochondria and Chloroplasts Are Eukaryotic Cytoplasmic Organelles Mitochondrial DNA Varies Widely in Size and Organization Chloroplast DNA Exhibits Many Properties of Eubacterial DNA Through Evolutionary Time, Genetic Information Has Moved Between Nuclear, Mitochondrial, and Chloroplast Genomes Damage to Mitochondrial DNA Is Associated with Aging Developmental Genetics and Immunogenetics Development Takes Place Through Cell Determination Pattern Formation in Drosophila Serves As a Model for the Genetic Control of Development Genes Control the Development of Flowers in Plants Programmed Cell Death Is an Integral Part of Development The Study of Development Reveals Patterns and Processes of Evolution The Development of Immunity Is Through Genetic Rearrangement Cancer Genetics Cancer Is a Group of Diseases Characterized by Cell Proliferation Mutations in a Number of Different Types of Genes Contribute to Cancer Changes in Chromosome Number and Structure Are Often Associated with Cancer Viruses Are Associated with Some Cancers Epigenetic Changes Are Often Associated with Cancer Colorectal Cancer Arises Through the Sequential Mutation of a Number of Genes Population Genetics Genotypic and Allelic Frequencies Are Used to Describe the Gene Pool of a Population The Hardy-Weinberg Law Describes the Effect of Reproduction on Genotypic and Allelic Frequencies Nonrandom Mating Affects the Genotypic Frequencies of a Population Several Evolutionary Forces Potentially Cause Changes in Allelic Frequencies Evolutionary Genetics Organisms Evolve Through Genetic Change Taking Place Within Populations Many Natural Populations Contain High Levels of Genetic Variation New Species Arise Through the Evolution of Reproductive Isolation The Evolutionary History of a Group of Organisms Can Be Reconstructed by Studying Changes in Homologous Characteristics Patterns of Evolution Are Revealed by Changes at the Molecular Level Reference Guide to Model Genetic Organisms
