Chapter 7: Structure and Replication of Genomes PDF

This PowerPoint will cover Chapter 7.  PLEASE NOTE: For the Chapter 7 content on Microbial Metabolism this week, you will be viewing the Publisher’s Videos in the Pearson Study Area. Instructions for Accessing These Videos from Pearson Study Area are below: To view these videos...

This PowerPoint will cover Chapter 7.  PLEASE NOTE: For the Chapter 7 content on Microbial Metabolism this week, you will be viewing the Publisher’s Videos in the Pearson Study Area. Instructions for Accessing These Videos from Pearson Study Area are below: To view these videos and animations: Access your Pearson Study Area. Click on Visualize Microbiology → click on Microbiology Animations with Quizzes → click on Microbial Genetics and Technology→ View EACH video under this link. Take the accompanying practice quizzes (non-graded items) to test your knowledge and understanding of the material. 2  Please view the following Publisher’s Videos in the Pearson Study Area for the remainder of content on Microbial Genetics. Please watch each video listed below. DNA Replication: Forming the Replication Fork DNA Replication: Overview DNA Replication: Replication Proteins DNA Replication: Synthesis Operons: Induction Operons: Overview Operons: Repression Transcription: Overview Transcription: The Process Translation: Overview Translation: The Genetic Code Translation: The Process Mutagens Mutations: Repair Mutations: Types Conjugation: Chromosome Mapping Conjugation: F Factor Conjugation: Hfr Conjugation Conjugation: Overview Horizontal Gene Transfer: Overview Transduction: Generalized Transduction Transduction: Specialized Transduction Transformation Transposons: Complex Transposons Transposons: Insertion Sequences Transposons: Overview  Course Learning Objective (CLO) CLO 1: Compare and contrast the cellular characteristics of the various prokaryotic and eukaryotic microorganisms (including helminths)  What is genetics? What is a genome? What is the Central Dogma of Molecular Biology? What is DNA? Guiding What is RNA? Questions What is a protein? What are the building blocks of DNA and RNA and proteins? What are the differences between prokaryotic and eukaryotic genomes?  How does DNA replication occur? How does RNA Transcription occur? How does protein translation occur? What is a plasmid? What is a mutation? What is the difference between phenotype and genotype? Guiding What is a gene? How are they regulated? What is transduction? How does it occur? Questions What is conjugation? How does it occur? What is horizontal gene transfer? How does it occur? The Structure and Replication of Genomes Genetics – Study of inheritance and inheritable traits as expressed in an organism’s genetic material Genome – The entire genetic complement of an organism – Includes its genes and nucleotide sequences The Structure and Replication of Genomes The Structure of Nucleic Acids – Polymers of nucleotides – Each nucleotide is made of Phosphate Pentose sugar Nitrogenous base – Length of DNA is expressed in base pairs Figure 7.1a-c The structure of nucleic acids. Figure 7.1d The structure of nucleic acids. For more information on nucleic acid structure click on the link below or watch The Structure of Nucleotides and The Structure and Function of Nucleic Acids videos in the Pearson Study Area https://mediaplayer.pearsoncmg.co m/assets/qtmwPtsKXvX0dOBwuW vQKhY_UYzDtcic https://mediaplayer.pearsoncmg.co m/assets/DvAuuBqU70ADKB6UCI 2tZAo1Z5He6EkE The Structure and Replication of Genomes The Structure of Prokaryotic Genomes – Prokaryotic chromosomes Main portion of DNA, along with associated proteins and RNA Prokaryotic cells are haploid (single chromosome copy) Typical chromosome is a circular molecule of DNA in the nucleoid Figure 7.2 Bacterial genome.  The Structure of Prokaryotic Genomes – Plasmids The Small molecules of DNA that replicate independently Structure Not essential for normal metabolism, growth, or and reproduction Replication Can confer survival advantages of Many types of plasmids: Genomes – Fertility factors – Resistance factors – Bacteriocin factors – Virulence plasmids  The Structure of Eukaryotic Genomes The – Nuclear chromosomes Structure Typically have more than one chromosome per cell and Chromosomes are linear and sequestered within Replication nucleus of Genomes Eukaryotic cells are often diploid (two chromosome copies) Figure 7.3 Eukaryotic nuclear chromosomal packaging. The Structure and Replication of Genomes The Structure of Eukaryotic Genomes – Extranuclear chromosomes of eukaryotes DNA molecules of mitochondria and chloroplasts – Resemble chromosomes of prokaryotes – Only code for about 5% of RNA and proteins Some fungi, algae, and protozoa carry plasmids Table 7.1 Characteristics of Microbial Genomes  Explains the flow of genetic information, from DNA → RNA Central →Protein. Dogma of Molecular Biology Proposed by Francis Crick in 1958.  The Structure and Replication of Genomes DNA Replication – Key to replication is the complementary structure of the two strands – Replication is semiconservative New DNA composed of one original and one daughter strand – Anabolic polymerization processes require monomers and energy Triphosphate deoxyribonucleotides serve both functions  Figure 7.4 Semiconservative model of DNA replication. Figure 7.5 The dual role of triphosphate deoxyribonucleotides as building blocks and energy sources in DNA synthesis.  DNA Replication Please watch the following video on DNA Replication (accessible via Pearson Study Area under the MicroFlix and BioFlix link): https://mediaplayer.pearsoncmg.com/asse ts/pmbbUonU74KKBtdbVdncS8F5QkOfm Umr Figure 7.6a DNA replication. Figure 7.6b-c DNA replication. The Structure and Replication of Genomes DNA Replication – Other characteristics of bacterial DNA replication Bidirectional Gyrases and topoisomerases remove supercoils in DNA DNA is methylated – Control of genetic expression – Initiation of DNA replication – Protection against viral infection – Repair of DNA Figure 7.7 The bidirectionality of DNA replication in prokaryotes.  Gene Function The Relationship Between Genotype and Phenotype – Genotype Set of genes in the genome – Phenotype Physical features and functional traits of the organism  Gene Function The Transfer of Genetic Information – Transcription Information in DNA is copied as RNA – Translation Polypeptides synthesized from RNA – Central dogma of genetics DNA transcribed to RNA RNA translated to form polypeptides Figure 7.8 The central dogma of genetics.  Gene Function The Events in Transcription – Six types of RNA transcribed from DNA RNA primers Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) Regulatory RNA Ribozymes  Gene Function The Events in Transcription – Occur in nucleoid of prokaryotes – Three steps 1. Initiation 2. Elongation 3. Termination Figure 7.9a The events in the transcription of RNA in prokaryotes. Figure 7.9b The events in the transcription of RNA in prokaryotes.  Gene Function The Events in Transcription – Transcriptional differences in eukaryotes RNA transcription occurs in the nucleus Transcription also occurs in mitochondria and chloroplasts Three types of nuclear RNA polymerases Numerous transcription factors Figure 7.11 Processing eukaryotic mRNA.  Gene Function Translation – Process in which ribosomes use genetic information of nucleotide sequences to synthesize polypeptides Figure 7.12 The genetic code.  Gene Function Translation – Participants in translation Messenger RNA Transfer RNA Ribosomes and ribosomal RNA Figure 7.13 Prokaryotic mRNA molecules typically lack introns and exons. Figure 7.14 Transfer RNA. Figure 7.15 Ribosomal structures. Figure 7.16 Assembled ribosome and its tRNA-binding sites.  Gene Function Translation – Events in translation Three stages of translation: – Initiation – Elongation – Termination – All stages require additional protein factors – Initiation and elongation require energy (GTP) Figure 7.17 The initiation of translation in prokaryotes. Figure 7.18 The elongation stage of translation. Figure 7.19 Polyribosome in prokaryotes— one mRNA and many ribosomes and polypeptides.  Gene Function Translation – Events in translation Termination – Release factors recognize stop codons » Modify ribosome to activate ribozymes – Ribosome dissociates into subunits – Polypeptides released at termination may function alone or together  Gene Function Translation – Translation differences in eukaryotes First amino acid is methionine rather than f- methionine Ribosomes can synthesize polypeptides into the cavity of the rough endoplasmic reticulum Table 7.2 Comparison of Genetic Processes  Gene Function Regulation of Genetic Expression – Most genes are expressed at all times – Other genes transcribed and translated when cells need them Allows cell to conserve energy  Mutation – Change in the nucleotide base sequence of a genome Mutations – Rare event of Genes – Almost always deleterious – Rarely leads to a protein that improves ability of organism to survive  Mutations of Genes Types of Mutations – Point mutations One base pair is affected Substitutions and frameshift mutations – Gross mutations Include inversions, duplications, and transpositions Figure 7.24 The effects of the various types of point mutations. Table 7.4 The Types of Point Mutations and Their Effects  Mutations of Genes Mutagens – Radiation Ionizing radiation Nonionizing radiation – Chemical mutagens Nucleotide analogs – Disrupt DNA and RNA replication Nucleotide-altering chemicals – Result in base-pair substitutions and missense mutations Frameshift mutagens – Result in nonsense mutations Figure 7.25 A pyrimidine (in this case, thymine) dimer. Figure 7.27 The action of a frameshift mutagen.  Mutations of Genes Frequency of Mutation – Mutations are rare events. Otherwise, organisms could not effectively reproduce. – Mutagens increase the mutation rate by a factor of 10 to 1000 times.  Mutations of Genes DNA Repair – Cells have numerous methods for repairing damaged DNA – Three categories: Direct repair Single-strand repair Error-prone repair Figure 7.28 DNA repair mechanisms. Mutations DNA Repair of Genes – Error-prone repair Induced when DNA damage is extensive Repair system of last resort SOS response in E. coli  Genetic Recombination and Transfer Horizontal Gene Transfer Among Prokaryotes – Horizontal gene transfer Donor cell contributes part of genome to recipient cell – Three types: Bacterial conjugation Transformation Transduction  Figure 7.35 Bacterial conjugation. Figure 7.36 Conjugation involving an Hfr cell.  Genetic Recombination and Transfer Horizontal Gene Transfer Among Prokaryotes – Transformation One of conclusive pieces of proof that DNA is genetic material Cells that take up DNA are competent – Results from alterations in cell wall and cytoplasmic membrane that allow DNA to enter cell Figure 7.33 Transformation of Streptococcus pneumoniae.  Genetic Recombination and Transfer Horizontal Gene Transfer Among Prokaryotes – Transduction Generalized transduction – Transducing phage carries random DNA segment from donor to recipient Specialized transduction – Only certain donor DNA sequences are transferred Figure 7.34 Transduction.  Friendly Reminder….. Your lab Midterm is next week