BYU11101 – From Molecules to Cells Lectures 1.1-1.5 PDF

BYU11101 – From Molecules to Cells (2024-2025). Section 1 Origins-Diversity-Cellular: Cellular Basis of Life Lecture 1 – What is Life? Dr Frederick Sheedy School of Biochemistry & Immunology  BYU11101 (Biology 101) CELLULAR BASIS &...

BYU11101 – From Molecules to Cells (2024-2025). Section 1 Origins-Diversity-Cellular: Cellular Basis of Life Lecture 1 – What is Life? Dr Frederick Sheedy School of Biochemistry & Immunology  BYU11101 (Biology 101) CELLULAR BASIS & CHEMISTRY OF BIOLOGICAL DIVERSITY OF LIFE LIFE INFORMATION School of Biochemistry & School of Immunology, Biochemistry & School of Genetics School of Microbiology Immunology 10 ECTS/credit module For every 1h lecture, ~5h student work  BYU11101 (Biology 101) CELLULAR BASIS & CHEMISTRY OF BIOLOGICAL DIVERSITY OF LIFE LIFE INFORMATION School of Biochemistry & School of Immunology, Biochemistry & School of Genetics School of Microbiology Immunology Luke O’Neill Frederick Sheedy Alistair Fleming The Origin of Life: Diversity of Life: Cellular Life: The microbial World… Biology intro Cell Structure Cell Division  BYU11101 (Biology 101) CELLULAR BASIS & CHEMISTRY OF BIOLOGICAL DIVERSITY OF LIFE LIFE INFORMATION School of Biochemistry & School of Immunology, Biochemistry & School of Genetics School of Microbiology Immunology LEARNING OUTCOMES: On successful completion of the module, students will be able to: 1. Provide an account of the cellular basis of life: from its origins in the abiotic world, to the evolution of unicellular and multicellular organisms. 2. Describe the diversity of life forms: including viruses, Prokaryotes (bacteria), Archaea, and Eukaryotes (unicellular organisms, animals and plants). WHAT IS BIOLOGY? WHAT IS BIOLOGY? Sept 2022 Sept 2024 WHAT IS BIOLOGY? COVID-19 Microbiology (Virology) understand the pathogen Immunology its interaction with our body Pathophysiology & Medicine the disease it causes + its treatment Genetics & Molecular Biology Sequence the genome –> diagnosis & therapeutics Immunology & Pharmacology Vaccines WHAT IS BIOLOGY? - the study of the organization, structure and function of living organisms  WHAT IS BIOLOGY? Levels of Organization in Biology: GLOBAL INDIVIDUALS MICROSCOPIC ATOMIC  WHAT IS BIOLOGY? Levels of Organization in Biology: GLOBAL Biosphere Disciplines of Biology: Ecosystems ECOLOGY Communities Populations ZOOLOGY BOTANY Organisms INDIVIDUALS Organs PHYSIOLOGY ANATOMY Tissues MICROBIOLOGY Cells CELL BIOLOGY MICROSCOPIC BIOCHEMISTRY Organelles GENETICS ATOMIC Molecules MOLECULAR BIOLOGY  WHAT IS BIOLOGY? BIOLOGY is not a stand-alone science: CHEMISTRY PHYSICS - The study of - The study of matter energy BIOLOGY - The study of living things MEDICINE MATHEMATICS - health-care - The study of practice numbers WHAT IS BIOLOGY? - the study of life WHAT IS LIFE?  WHAT IS LIFE? PHILOSOPHICAL BIOLOGICAL QUESTION QUESTION  WHAT IS LIFE? “All life is born from chaos” ORDER -> DISORDER (Physics/Thermodyamics) DISORDER -> ORDER (Life/Schrodinger) /CHAOS WHAT IS LIFE?  WHAT IS LIFE? “ how can the events in space & time, which take place within the spatial boundaries of a living organism, be accounted for by physics and chemistry”  WHAT IS LIFE? “Genetic Information contained within APERIODIC CRYSTAL via covalent chemical bonds between various crystal/soluble states”  WHAT IS(’NT) LIFE? This article was originally published with the title "Life as We Don't Know It" in Scientific American 328, 2, 32-39 (February 2023) doi:10.1038/scientificamerican0223-32 https://www.scientificamerican.com/article/the-search-for-extraterrestrial-life-as-we-dont- know-it/  Variation in Life forms Fungi Bacteria Viruses Animals Plants  Features of Living Organisms Adaptation Order/Organization Responsiveness Control/Regulation Reproduction Obtain/Use Energy & Heredity Growth  Molecular Processes Adaptation Order/Organization Responsiveness Control/Regulation Reproduction Obtain/Use Energy & Heredity Growth REPLICATION METABOLISM  Self-Replication - as the defining feature of life? Animals Plants Bacteria ORGANISMAL LEVEL  Self-Replication - as the defining feature of life? Animals Plants Bacteria ORGANISMAL LEVEL ???? Viruses Computer Robots/AI code/virus  Self-Replication - as the defining feature of life? Animals Plants Bacteria ORGANISMAL LEVEL Proteins ??? DNA MOLECULAR LEVEL  Self-Replication - as the defining feature of life? Animals Plants Bacteria ORGANISMAL LEVEL Proteins ??? DNA MOLECULAR LEVEL  Self-Replication - as the defining feature of life? Genes/DNA as “replicators”, Organisms as “vehicles”, Human/Animal behavior promotes replication  Self-Replication - as the defining feature of life?  Self-Replication - as the defining feature of life?  The Cell - the molecular machine which allows Self-Replication?  The Cell - the molecular machine which allows Energy Generation Energy Generation - the molecular process which allows Self-Replication  The Cell - the molecular machine which allows Energy Generation Energy Generation - the molecular process which allows Self-Replication  How did all this come together & WHEN The Origin of Life aka THE BIGGEST RIDDLE OF THEM ALL https://www.rte.ie/player/series/earth/10002724-00-0000?epguid=AQ10002725-01-0002  Theories on The Origin of Life Life Continuously Life Continuously “Arises” “Evolves” (from Non-Living Things) (from Living Things) “Spontaneous Generation” “Darwinian Evolution”  Theories on The Origin of Life Life Continuously Life Continuously “Arises” “Evolves” (from Non-Living Things) (from Living Things) “Spontaneous Generation” “Darwinian Evolution” OBSERVATION VERSUS EXPERIMENTATION  Theories on The Origin of Life ABIOGENESIS: Non Continuously/Spontaneously Occurring Non-Living Things -> Living Things BIOGENESIS: Continuously Occurring Living Things -> Living Things  Theories on The Origin of Life ABIOGENESIS: Not Continuously/Spontaneously Occurring Non-Living Things -> Living Things BIOGENESIS: Continuously Occurring (The Tree of Life) Living Things -> Living Things EXCEPT ABIOGENESIS: Non-Living Things -> Living Things It had to start somewhere…./some-when  Theories on The Origin of Life ABIOGENESIS: Not Continuously/Spontaneously Occurring Non-Living Things -> Living Things BIOGENESIS: Continuously Occurring (The Tree of Life) Living Things -> Living Things EXCEPT PANSPERMIA: Extra-Terrestrial -Living Things -> Terrestrial Living Things https://astrobiology.nasa.gov/news/in-search-of-panspermia/  The Origin of Life “Timeline” INNOVATION/DRIVEN BY GEOLOGICAL CHANGES/EVENTS CHEMICAL CHANGES/EVENTS BIOLOGICAL CHANGES/EVENTS  Early Earth 4.54 BYA Temperature - Reducing (no O2) - Other Gases – Water? - 3.8 BYA PRESENT DAY  The First Rain Fossil Record indicates liquid water between 4.2- 3.8 BYA Consistent with cooling of atmosphere  The First Rain Terrestrial Source (H2 interacting with magma) Fossil Record indicates liquid water between 4.2- 3.8 BYA Extra-Terrestrial Consistent with cooling of Source (Asteroids) atmosphere  The First Rain Terrestrial Source (H2 interacting with magma) Fossil Record indicates liquid water between 4.2- 3.8 BYA Extra-Terrestrial Consistent with cooling of Source (Asteroids) atmosphere Water (H20) – is key solvent for biological life; - Cohesion of water molecules - Moderate temperature - Allow Floating - Aqueous solutions/Solvent (aka MEDIUM for Life) Other substances dissolve in it Some substances repel it & form “BARRIERS’ Key to opposing Thermodynamics [Ch3 Campbell]  Prebiotic Conditions Can Give Rise to Biotic Molecules - Experiment Miller Experiment (Fig 4.2, Campbell) - Simulated early-earth (prebiotic) conditions, atmosphere [gases], liquid water, temperature & energy, (closed conditions) - Took Samples for analysis => KEY READOUT – the presence of Amino Acids (precursors of proteins), also detected purines & pyrimidines (nucleic acids)  1953; Link between DNA & Amino Acids emerges Watson, Crick & Franklin Miller Experiment Molecular Structure of DNA Highlight measured Amino Acids Instructions for Proteins (Precursors of Proteins)  Updated Hypothesis? Refining the Experiment Patel et al Experiment - More accurately simulated prebiotic conditions (gases, UV light)  READOUT; measured 3 key ingredient for Cells  (Cells in a blender -> Nucleotides, Amino Acids  But also LIPIDS (separation from environment) Key to opposing Thermodynamics  Not Just DNA; What Came Before THE RNA WORLD Idea The RNA world: RNA can act as an informational polymer but also an enzyme to promote Self Replication In more unstable prebiotic conditions, RNA was superior biological polymer => DNA evolved, more stable & became protected as Cells evolved EVIDENCE: - RNA viruses, mRNA? (It can be the sole source of genetic information) - Ribozymes, The Ribosome (It can be the catalyst for metabolic reactions)  The First Evidence of Cellular Life Stromatolites Living Fossil Record of earliest forms of oceanic life Aquatic (ocean-living) progenitors of Cyanobacteria - Likely preceeded by simpler life which used C02 & other gases to make CH4 (Methane) Cyanobacteria make Food/Early Biomolecules & O2 from H20 & CO2 (Early photosynthesis) Production of O2 transformed the planet & evolution of life  The Origin of Life “Timeline” INNOVATION/DRIVEN BY GEOLOGICAL CHANGES/EVENTS CHEMICAL CHANGES/EVENTS BIOLOGICAL CHANGES/EVENTS  After the First Cells & Photosynthesis; => Endosymbiosis * Key Steps Early photosynthetic bacteria (Cyanobacteria) Early Aerobic bacteria, can use oxygen Division of Labor & primitive nucleus forming* 1st STEP in Endosymbiosis; Aerobic bacteria enters primitive eukaroytic cell 2nd STEP in Endosymbiosis Endosymbiotic relationship with photosynthetic bacteria established Last Common Ancestor of Animals split from Plants before 2nd Step (Evidence – we lack Chloroplasts & evolved our bodies around obtaining Food) After the First Cells & Photosynthesis; => Endosymbiosis  After Endosymbiosis; => Multi-cellularity Obtaining Food & Reproduction drove evolution; - Amoeba (single cell eukaryotic ‘animal’) - Slime Mould (Dictosytelium) – sexual reproduction - Sea Sponge (Hydra) - cell specialization [prey]  Recap Lecture 1 (Previous): Module/Course overview What is Biology What is Life The Origin of Life  FURTHER READING CAMPBELL BIOLOGY - Essential Biology Textbook - Ch's 1, 3-4 The Selfish Gene – Richard Dawkins The Vital Question – Nick Lane Notes on Blackboard https://www.scientificamerican.com/article/the-search-for-extraterrestrial- life-as-we-dont-know-it/ BBC's EARTH (with Chris Packham?) - RTE Player Contact: [email protected], Twitter; @Fredtwee & Good Luck BYU11101 – From Molecules to Cells (2022-2023). Section 1 Origins-Diversity-Cellular: Cellular Basis of Life Lecture 2; Cellular Organization Dr Frederick Sheedy School of Biochemistry & Immunology  Cells come in all shapes & sizes Animal Cell Bacterial Cell Plant Cell Fungal Cell Neurons Muscle Cell TISSUES Cells are made of Bio-molecules ELEMENTS: C Carbon –based lifeforms, Carbon backbone of all molecules (hydrocarbons = organic chemistry) H Hydrogen - bonding, part of water O -Oxygen - is life N Nitrogen - nitrogenous bases & amine group P Phosphorous – energy carrier & backbone of DNA S Sulfur – disulphide bonds H20; WATER – solvent for life  Cells are made of Bio-molecules ELEMENTS: C Carbon –based lifeforms, Carbon backbone of all molecules (hydrocarbons = organic chemistry) H Hydrogen - bonding, part of water HYDROPHILIC Water Loving O -Oxygen - is life Dissolve/Mix in water N Nitrogen - nitrogenous bases & amine group P Phosphorous – energy HYDROPHOBIC carrier & backbone of DNA (or Hydrophobicity) Water-hating S Sulfur – disulphide bonds Will not mix with water H20; WATER – solvent for life Cells are made of Bio-molecules Nucleic Acids Proteins DNA - genetic material - Products of genes - The Selfish Gene - Catalysts to promote replication RNA - messenger Lipids Carbohydrates - Give structure - Provide energy for growth & replication - Provide barriers - Give structure Cells are made of Bio-molecules Nucleic Acids Proteins DNA - genetic material - Products of genes - The Selfish Gene - Catalysts to promote replication RNA - messenger Lipids Carbohydrates - Give structure - Provide energy for growth & replication - Provide barriers - Give structure  Cellular Life What is life? The capacity for GROWTH & SELF-REPLICATION Processes: Biomolecules:  Cellular Life What is life? The capacity for GROWTH & SELF-REPLICATION METABOLISM Processes: MAINTAIN ORDER INHERITANCE OF RESPOND TO STIMULI GENETIC MATERIAL Biomolecules:  Cellular Life What is life? The capacity for GROWTH & SELF-REPLICATION METABOLISM Processes: MAINTAIN ORDER INHERITANCE OF RESPOND TO STIMULI GENETIC MATERIAL PROTEINS CARBOHYDRATES NUCLEIC ACIDS – Biomolecules: DNA/RNA LIPIDS  Cellular Life What is life? The capacity for GROWTH & SELF-REPLICATION METABOLISM Processes: MAINTAIN ORDER INHERITANCE OF RESPOND TO STIMULI GENETIC MATERIAL PROTEINS CARBOHYDRATES NUCLEIC ACIDS – Biomolecules: DNA/RNA LIPIDS Alterations: EVOLUTION VARIATION IN LIFE-FORMS  The Central Dogma of Molecular Biology THE TRANSMISSION OF GENETIC INFORMATION Biomolecules: Processes: Function: Genetic material DNA Self-replicating molecule “Selfish Gene” instructions for cellular life Temporary copy of DNA Expresses the instructions RNA for life ”Messenger” Catalysts for Cellular Life (Metabolism) PROTEINS Effectors  The Central Dogma of Molecular Biology THE TRANSMISSION OF GENETIC INFORMATION Biomolecules: Processes: Function: Replication of DNA Genetic material DNA Self-replicating molecule “Selfish Gene” instructions for cellular life Transcription of DNA Temporary copy of DNA Expresses the instructions RNA for life ”Messenger” Translation of RNA Catalysts for Cellular Life (Metabolism) PROTEINS Effectors  The Central Dogma of Molecular Biology TRANSMISSION OF GENETIC INFORMATION THE CATALYTIC EVENTS SUPPORTING THE THE TRANSMISSION OF GENETIC INFORMATION Biomolecules: Processes: Replication of DNA DNA Metabolism Growth Transcription of DNA Response to Stimuli RNA Translation of RNA PROTEINS  The Central Dogma of Molecular Biology THE TRANSMISSION OF GENETIC INFORMATION TRANSMISSION OF GENETIC INFORMATION THE CATALYTIC EVENTS SUPPORTING THE Biomolecules: Processes: Replication of DNA DNA Metabolism Growth Transcription of DNA Response to Stimuli RNA Translation of RNA PROTEINS TRANSMISSION OF GENETIC INFORMATION & PROCESSES TO SUPPORT THIS ARE FACILITATED BY CELL STRUCTURE  Common features of Cells NUCLEAR REGION contains genetic material (DNA) Allows DNA Replication & DNA Transcription (DNA + RNA + PROTEIN) PLASMA MEMBRANE separates cell from outside maintains order allows transport (LIPID + PROTEIN) CYTOPLASM Contains multiple organelles & sites of catalytic action to support metabolic activities required for growth & replication  Human skin cell Frog pigment cell Imaged by Light Microscopy Imaged by Fluorescent Confocal Microscopy Low resolution High resolution Need to decipher contents Labelling of contents Light powered Laser-powered Hierarchy to Cell Structure NUCLEUS ‘Administrative capital of the cell Contains, Protects, decides & sends out the instructions for cell behavior DNA -> RNA * Evolution of a nucleus (Internal membranes) was first step to Compartmentalization of cells to diversify & specialize functions  The Tree of Life NUCLEAR REGION NUCLEUS genetic information in cytoplasm Genetic information (DNA) contained within nuclear membrane separated from cytoplasm PROKARYOTES EUKARYOTES no true/before nucleus true nucleus (NUCLEOID)  The Tree of Life - 3 Domain System Bacteria Domain ARCHAEA formerly known as no true nucleus “Eubacteria” More closely related to Eukaryotes than Prokaryotes based on “phylogenetic sequencing” of rRNA  Modifying the 3 Domain System (Eu)-Bacteria Archaea no true nucleus no true nucleus EUKARYA Fatty acids + ester Fatty acids + ether True nucleus linkages linkages Membrane bound rRNA rRNA – distant from organelles eubacteria rRNA Bacteria + Archaea = PROKARYOTES  Modifying the 3 Domain System ASGARD ARCHAE (Eu)-Bacteria Archaea no true nucleus no true nucleus EUKARYA Fatty acids + ester Fatty acids + ether True nucleus linkages linkages Membrane bound rRNA rRNA – distant from organelles eubacteria rRNA Bacteria + Archaea = PROKARYOTES  2 Groups 7 Kingdoms Photosynthetic uni/multi-cellular unicellular eukaryotic non-plants eg – microbes eg – some some algae Amobea  Prokaryotes Versus Eukaryotes PROKARYOTES EUKARYOTES no true nucleus true nucleus Nuclear region called “Nucleoid” DNA Within nucleus, nucleolus region no membrane separating it Membrane-enclosed No membrane-bound organelles – Contain organelles (eg-Mitochondria) metabolism in cytoplasm & internal membranes;“Division of labor” Cell Wall gives structure & rigidity No Cell Wall – more fluidic shape Smaller cells 1-5 μM Larger cells 10-50 μM Note on Cell Size (Surface Area:Volume Ratio) A. B. C. Calculate the surface area to volume ratio for each. Smaller cells working together overcomes Surface Area:Volume problem For the following Eukaryotic organisms, suggest ways in which they have overcome the surface area : volume ratio problem - Fungal hyphae - Eukaryotic muscle tissue - Plant cell  Recap Lecture 2 (Recap): Biomolecules (Intro) Information Flow in Biology General Cell Structure The Tree of (Cellular) Life Pro Versus Eukaryotic Cells  BYU11101 – From Molecules to Cells. Section 1 Origins-Diversity-Cellular: Cellular Basis of Life Lecture 3; The Nucleus Dr Frederick Sheedy School of Biochemistry & Immunology Prokaryotes Versus Eukaryotes?? Prokaryotes Versus Eukaryotes?? Prokaryotes Versus Eukaryotes?? The Nucleus/Nuclear Region Nucleus (DAPI), Cytoplasm (Actin stain) The Nucleus: CHROMOSOMES # contains DNA packaged with proteins called chromatin #Only visible in replicating cells NUCLEOLUS* area rich in ribosomal RNA *obvious under microscope NUCLEAR ENVELOPE Two phospholipid bi-layer’s form the Nuclear Membrane Studded with Nuclear Pores Allows transport of RNA out & signals inward…  The Nuclear Envelope Pore complexes (TEM) Nuclear Envelope: (2 bi-layers) Outer membrane Inner Membrane Nuclear pore Pores, lined with a structure called a pore complex, regulate the entry and Surface of nuclear exit of molecules from the nucleus envelope (TEM – Transmission Electron Microscopy) The nuclear side of the envelope is lined by the nuclear lamina, which is composed of proteins and maintains the shape of the nucleus  DNA THE DOUBLE HELIX: sugar-phosphate backbone 2 strands of ‘complementary’ DNA => dsDNA helix Hydrogen-bonded base pairs DOUBLE HELIX STRUCTURE ALLOWS: - DNA REPLICATION – whole genome unwinding & copying chromosomes - DNA TRANSCRIPTION – regulated unwinding of specific genetic sequences/genes, creation of “RNA” copy  Nuclear Proteins in Eukaryotes DNA HISTONE PROTEIN NUCLEOSOMES CHROMATIN CHROMOSOMES DNA, Chromosomes -> The Genome THE GENOME IS THE BOOK OF LIFE DNA bases – Letters DNA strands – Sentences Genes – “Dialog/Action Words” Chromosomes – 1 Chapter, contains many genes “dialog” & sentences that give these context “Regulatory DNA” Our Genome - BOOK Blueprint for Life YEAR 2000 – MAJOR DEVELOPMENTS  BioFlix: Tour of an Animal Cell Play from 1:27→ 2:10 mark, “Enter the nucleus & DNA packaging”.  Reading the DNA - Transcription Template: Catalyst: Product: RNA polymerase (protein enzyme) DNA messenger RNA (Gene) RNA nucleotides (mRNA) DNA RNA SUGAR COMPONENT – SUGAR COMPONENT – Deoxyribose “D in DNA” Ribose “R in RNA” Thymine as base URACIL as base Stable Structure Unstable, short-lived double stranded single strand  Reading the DNA - Transcription Template: Catalyst: Product: RNA polymerase (protein enzyme) DNA messenger RNA (Gene) RNA nucleotides (mRNA) The Fate of RNA.. mRNA “Translated” into proteins Exported from Nucleus To sites of PROTEIN SYNTHESIS - RIBOSOMES  The Fate of RNA.. mRNA “Translated” into proteins amino acid Exported from Nucleus attached to tRNA molecule To sites of PROTEIN SYNTHESIS - RIBOSOMES rRNA tRNAs ribosomal RNA transfer RNAs Forms a complex with proteins RNA species that links up with – RIBOSOME AMINO ACIDS -> PROTEINS Site of protein synthesis Found in Ribosomes  Lost in Translation ? Template: Catalyst: Product: RIBOSOME (protein & RNA complex) mRNA Protein (Nucleotides) rRNA + tRNA (Amino Acids) The Ribosome Ribosomes: Found in pro & eu-karyotes Central in flow of genetic information Translate mRNA into PROTEINS Complex of rRNA, proteins, tRNA & mRNA Found free in cytoplasm Or associated with Endoplasmic Reticulum (ER) – membrane network from nucleus into cell  0.25 μm Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER TEM showing ER and ribosomes  BioFlix: Tour of an Animal Cell Play from 2:10 → 2:42 mark, “RNA->Protein”. Proteins are Key Cellular Effectors  => LIFE Fungi Bacteria Viruses Animals Plants  Recap Lecture 3 (Recap): Pro Versus Eukaryotic Cells Nucleus/Nuclear Region DNA & The Genome RNA & Ribosomes  BYU11101 – From Molecules to Cells. Section 1 Origins-Diversity-Cellular: Cellular Basis of Life Lecture 4; Beyond the Nucleus Dr Frederick Sheedy School of Biochemistry & Immunology  Recap NUCLEUS DNA resides mRNA made CYTOPLASM (Ribosome) mRNA translated into PROTEIN  Beyond the Nucleus CYTOPLASM: Area defined by nuclear membrane & plasma membrane Consists of CYTOSOL + membrane-bound ORGANELLES  Cytosol Intracellular fluid inside the cell (transparent) Mainly water, ions, biomolecules/metabolites & proteins Concentration Gradients of Biomolecules - metabolism Protein Complexes (Inflammasomes/Apoptosomes/Centrosomes) – cell signalling/division -Free Ribsomes CYTOSKELETON proteins - Shape, Structure & Motility Cytoskeleton ACTIN FILAMENTS: Aka Microfilaments, “Actin” polymers, Cellular growth as actin filaments polymerizes & depolymerizes at opposite ends “Myosin” binds & “moves” along INTERMEDIATE FILAMENTS: Larger filament structures, Various proteins – cell-type specific, Eg – “Keratin” in epithelia Anchor organelles & organize 3-D shape MICROTUBULES: Hollow cylinder structure, “Tubulin” polymers, Involved in cellular organization & Centrosome  Where do the proteins go? - The Endomembrane System  The Endomembrane System The endomembrane system consists of – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane These components are either continuous or connected via transfer by vesicles The endomembrane system is a complex and dynamic player in the cell’s compartmental organization The Endoplasmic Reticulum Endoplasmic Reticulum Membrane network from nucleus into cell Consists of folds – Cisternae Rough ER – studded with Ribosomes, sites of protein synthesis & modification (glycoproteins) Smooth ER – no Ribosomes, important in Lipid synthesis & detoxification Lipid + Protein Synthesis -> Membrane Factory The Endoplasmic Reticulum Endoplasmic Reticulum Membrane network from nucleus into cell Consists of folds – Cisternae Rough ER – studded with Ribosomes, sites of protein synthesis & modification (glycoproteins) Smooth ER – no Ribosomes, important in Lipid synthesis & detoxification Q - Where does it lead? It doesn’t reach plasma membrane directly Vesicles bud off – (membrane bound) & transport contents around & out of cell [Sorting & Packaging Function]  Intracellular Transport Golgi Apparatus: Directs/Sorts traffic inside the cell Smooth ER – traffics lipid (steroid hormones/membrane) to GOLGI Rough ER Vesicles – delivers protein cargo to GOLGI New membrane-bound organelles/Vesicles bud off GOLGI Go to… ENDO-LYSOSOME – for recycling PLASMA MEMBRANE –for Transport Functions The Golgi Apparatus Golgi Vessel/Apparatus Membrane network within cytoplasm Generally 4-8 folds/sacs-Cisternae (ER-derived) Cis face – nuclear “receiving” side Trans face – plasma membrane “shipping” side Directs & sorts trafficking of proteins within & out of the cell via the PLASMA MEMBRANE  Cellular Transport - Out SECRETION ENDOCYTOSIS Aka Exocytosis  Cellular Transport - In ENDOCYTOSIS Cellular Transport - In The Lysosome Membrane bound compartment within the cell Highly acidic Contains degradative (hydrolytic) enzymes (work at acidic pH) – made in rER, bud off & acidify -> LYSOSOME Cargo delivered to LYSOSOME => DEGRADATION Integrates Transport Network from ER/Golgi (Vesicles) & Endosomes (incoming cargo from external environment or cytoplasm) Important in response to external cargo eg-food/pathogens (PHAGOCYTOSIS) Important in recycling old organelles within cytoplasm (AUTOPHAGY)  The Lysosome Membrane bound compartment within Digestive the cell Lysosome enzymes Highly acidic Plasma membrane Digestion Contains degradative (hydrolytic) Food enzymes (work at acidic pH) – made in vacuole rER, bud off & acidify -> LYSOSOME (a) Phagocytosis Cargo delivered to LYSOSOME => DEGRADATION Integrates Transport Network from ER/Golgi (Vesicles) & Endosomes Lysosome (incoming cargo from external Peroxisome environment or cytoplasm) Important in response to external cargo Mitochondrion Digestion Vesicle eg-food/pathogens (PHAGOCYTOSIS) (b) Autophagy Important in recycling old organelles within cytoplasm (AUTOPHAGY)  Animation: Lysosome Formation © 2018 Pearson Education Ltd.  Video: Phagocytosis in Action © 2018 Pearson Education Ltd.  The Plasma Membrane WE HAVE REACHED OUR FINAL DESTINATION FOR TODAY  Common features of Cells NUCLEAR REGION PLASMA MEMBRANE separates cell from outside maintains order allows transport (LIPID + PROTEIN) CYTOPLASM The Plasma Membrane KEEP WHITE WALKERS INVADERS OUT MAINTAIN ORDER WITHIN  The Plasma Membrane - separates cell from outside environment - maintain order & organization Q – How do you chemically achieve this?? PROBLEM: Cytoplasm – mainly water, Hydrophilic environment Proteins (Water soluble) Some nucleic acids (RNA) Need something that won’t mix with these to provide separation  The Plasma Membrane - separates cell from outside environment - maintain order & organization Q – How do you chemically achieve this?? PROBLEM: Cytoplasm – mainly water, Hydrophilic enviroment Proteins (Water soluble) Some nucleic acids (RNA) Need something that won’t mix with these to provide separation (NON-POLAR) (Hydrophobic)  Lipids provide the “solution” LIPIDS: a diverse group of biochemicals contain carbon-hydrogen chains/rings confers rigid structure  INSOLUBLE in Water “Hydrophobic” “Non-Polar” aka Water-hating Common feature is (in)solubility, not structure  Lipids provide the “solution” LIPIDS: a diverse group of biochemicals contain carbon-hydrogen chains/rings confers rigid structure  INSOLUBLE in Water “Hydrophobic” “Non-Polar” aka Water-hating Common feature is (in)solubility, not structure Lipids can have hydrophobic & hydrophilic portions (amphipathic) Ideal for use in membranes The Phospho-lipid bi-layer PHOSPHO-LIPID: amphipathic lipid species – contains hydrophobic and hydrophilic portions PHOSPHATE HEAD – water soluble/hydrophilic/polar 2 FATTY ACID (C/H chain) tails – hydrophobic/non-polar, insoluble eg – phosphatidylcholine Q – What happens when phospholipids get together ???  The Phospho-lipid bi-layer BI-LAYER: Flat-sheet containing 2 layers of phospholipids Hydrophobic tails attracted to each other Exposes the Hydrophilic Heads to the external and internal water soluble environments Hydrophobic tails provide separation Hydrophilic Heads allow mixing with the environment Plasma membrane terminus for eukaryotes, Prokaryotes have more "layers" PROKARYOTES EUKARYOTES no true nucleus true nucleus Nuclear region called “Nucleoid” no DNA Within nucleus, nucleolus region membrane separating it Membrane-enclosed No membrane-bound organelles – Contain organelles (eg - Mitochondria) metabolism in cytoplasm & internal membranes; “Division of labor” Cell Wall gives structure & rigidity No universal Cell Wall – more fluidic shape *Exception; plants/fungi Smaller cells 1-5 μM Larger cells 10-50 μM  Bacterial Cell Wall Provides extra support Contains many lipid, lipoprotein, carbohydrate/sugar species Some bacteria have second “plasma membrane” outside their cell wall Allows more specificity/selectivity Cell Wall & Membrane components often associated with immunogenicity and pathogenicity Targeted by antibiotics Some structures derived – flagella/pillae involved with movement or attachment to substrates Some bacteria possess polysaccharide CAPSULE outside cell wall or develop tougher structures for survival (SPORES) Bacterial kingdom divided into 2 Groups based on Cell Wall Structure & how they stain under biochemical assays (Gram stain)  Gram Negative Vs Gram Positive GRAM NEGATIVE GRAM POSITIVE Contain outer membrane with lots of No outer membrane lipids/lipoprotein & transport proteins Major Peptidoglycan (carbohydrate Thin cell wall of peptidoglycan polymer) cell wall (stain negative) (Stain positive – retain counterstain) Contains periplasmic space Smaller periplasmic space Animal Vs Plant Cells PLANT CELLS Have a thick cellulose cell wall (carbohydrate polymer) Confers stability & protection Survive high osmotic pressure Plant Cell Wall PLANT CELLS Neighboring cell walls exist side by side Each has a 3-layer structure - Plasma membrane (inside) - 3 layers of cellulose “primary wall” - Outer “middle lamella”, forms the division/border with neighboring cell  Prokaryotes Versus Eukaryotes PROKARYOTES EUKARYOTES no true nucleus true nucleus Nuclear region called “Nucleoid” DNA Within nucleus, nucleolus region no membrane separating it Membrane-enclosed No membrane-bound organelles – Contain organelles (eg-Mitochondria) metabolism in cytoplasm & internal membranes;“Division of labor” Cell Wall gives structure & rigidity No Cell Wall – more fluidic shape Smaller cells 1-5 μM Larger cells 10-50 μM  Prokaryotes Versus Eukaryotes MITOCHONDRIA CHLOROPLASTS All free-living eukaryotes Plants & Algae only Double membrane system Double membrane system (similar to prokaryotic cells) (similar to prokaryotic cells) Inner membrane – folds “Cristae” Contain “Chlorophyll” chemical in Own DNA & Ribosomes in “Mitochondrial internal membrane network “Thylakoids” matrix” Own DNA & Ribosomes in “Stroma” Allows cellular respiration, Breakdown of Glucose (cytoplasm) & Allows Photosynthesis, other intermediates (matrix) to generate Captures light energy, fuel enzymatic energy via oxidative phosphorylation formation of Glucose (req CO2/H20), (cristae - req O2) generates O2 Prokaryotes Endoplasmic Versus Nucleus Eukaryotes reticulum earliest step in eukaryotic cell evolution Nuclear envelope Engulfing of oxygen- using nonphotosynthetic prokaryote, which becomes a mitochondrion Ancestor of eukaryotic cells (host cell) Mitochondrion Engulfing of photosynthetic prokaryote Chloroplast At least Mitochondrion one cell Nonphotosynthetic eukaryote Photosynthetic eukaryote  Cellular Compartmentalization Fig X.xx Campbell Biology & Integrated Assignment Worksheet  Recap Lecture 4 The Cytoplasm, Cytosol & Cytoskeleton The Transmembrane Network - Endoplasmic Reticulum/The Golgi Lysosomes & Recycling The Plasma Membrane Cell Walls Organelles with prokaryotic origin & metabolic function  BYU11101 – From Molecules to Cells. Section 1 Origins-Diversity-Cellular: Cellular Basis of Life Lecture 5; Cell Division Dr Frederick Sheedy School of Biochemistry & Immunology Cell Division – facilitating Self-Replication Levels of “Replication” Replication & Duplication of DNA Types of Cell Division Mitosis Cytoplasmic Events in Replication Stages of Cell Division & Regulation Special Forms of Cell Division (Meiosis)  Levels of Replication The Cell – the Molecular Machine for Self-Replication? Replication of DNA DNA Cellular Growth, Expansion & Division PROTEINS LIPIDS  Replication of DNA THE DOUBLE HELIX: sugar-phosphate backbone 2 strands of ‘complementary’ DNA => dsDNA helix Hydrogen-bonded base pairs DOUBLE HELIX STRUCTURE ALLOWS: - DNA REPLICATION – whole genome unwinding & copying chromosomes - DNA TRANSCRIPTION – regulated unwinding of specific genetic sequences/genes, creation of “RNA” copy  DNA Replication -> Chromosome Organization DNA HISTONE PROTEIN NUCLEOSOMES CHROMATIN CHROMOSOMES  DNA Replication -> Chromosome Organization DNA HISTONE PROTEIN Only appears like this after “DNA REPLICATION” SISTER NUCLEOSOMES CHROMATIN CHROMATIDS  VIDEO illustrating CHROMSOMAL DUPLICATION PLAY FROM 0:20 sec to 1:00 min mark…  Chromosomal Duplication 1 Chromosomes Chromosomal DNA molecules Centromere Chromosome arm Chromosome duplication Replication of DNA 2 DNA Centromere – anchors chromatids Sister chromatids Separation of sister chromatids 3 DNA Replication – 1 side of the story… Replication of DNA DNA Cellular Growth, Expansion & Division PROTEINS LIPIDS Nuclear & Cytoplasmic Events allow Seperation  Types of Cell Division - DNA REPLICATION – central to ‘all’ Cell Division - Different Cells have different STRUCTURES - DNA is organized very differently in different CELLS - => Different Types of Cell Division Bacterial Kinetochore chromosome microtubule Intact nuclear envelope (a) Bacteria No nucleus (c) Diatoms and some yeasts 1 “bacterial chromosome” Chromosomes Duplicates by replication Kinetochore Microtubules Cell divides around this microtubule “BINARY FISSION” Intact nuclear Fragments of envelope nuclear envelope (b) Dinoflagellates (d) Most eukaryotes  Types of Cell Division - DNA REPLICATION – central to Cell Division - Different Cells have different STRUCTURES - DNA is organized very differently in different CELLS - => Different Types of Cell Division Bacterial Kinetochore chromosome Bacterial microtubule Kinetochore chromosome microtubule Intact nuclear envelope Intact nuclear envelope (a) Bacteria (c) Diatoms and some yeasts (a) Bacteria (c) Diatoms and some yeasts “BINARY FISSION” Chromosomes Have nuclei Chromosomes Kinetochore & chromosomeKinetochore (s) Microtubules microtubule Microtubules Cell Walls microtubule Nuclear envelope remains Fragments of intact Intact nuclear nuclear Intact nuclearChromosomes duplicates Fragments&of envelope envelope envelope nuclear (b) Dinoflagellates (d) Most eukaryotes separate envelope (b) Dinoflagellates (d) Most eukaryotes “BINARY FISSION/BUDDING”  Types of Cell Division - DNA REPLICATION – central to Cell Division - Different Cells have different STRUCTURES - DNA is organized very differently in different CELLS - => Different Types of Cell Division Bacterial Have nuclei Kinetochore chromosome Bacterial microtubule Kinetochore & multiple chromosomes chromosome microtubule Bacterial No Cell Walls Kinetochore Intact nuclear chromosome Nuclear envelope dissolves microtubule envelope Intact nuclear envelope Chromosomes duplicates & (a) Bacteria (c) Diatoms and some yeasts separate Intact (a) Bacteria nuclear envelope (c) Diatoms and some yeasts “BINARY FISSION” Chromosomes Cell divides around this “BINARY (a) Bacteria (c) Diatoms and Chromosomes some yeasts Nuclear envelope re-forms Kinetochore FISSION/BUDDING” Microtubules microtubule Kinetochore Chromosomes “MITOSIS” Microtubules microtubule Kinetochore Microtubules microtubule Intact nuclear Fragments of nuclear Intact nuclear Fragments of envelope envelope envelope nuclear (b) Dinoflagellates (d) Most eukaryotes envelope Intact nuclear (b) Dinoflagellates Fragments of (d) Most eukaryotes envelope nuclear envelope (b) Dinoflagellates (d) Most eukaryotes  Types of Cell Division - DNA REPLICATION – central to Cell Division - Different Cells have different STRUCTURES - DNA is organized very differently in different CELLS - => Different Types of Cell Division Bacterial Have nuclei Kinetochore chromosome Bacterial microtubule Kinetochore & multiple chromosomes chromosome microtubule Bacterial No Cell Walls Kinetochore Intact nuclear chromosome Nuclear envelope dissolves microtubule envelope Intact nuclear envelope Chromosomes duplicates & (a) Bacteria (c) Diatoms and some yeasts separate Intact (a) Bacteria nuclear envelope (c) Diatoms and some yeasts “BINARY FISSION” Chromosomes Cell divides around this “BUDDING” (a) Bacteria (c) Diatoms and Chromosomes some yeasts Nuclear envelope re-forms Kinetochore Microtubules microtubule Kinetochore Chromosomes “MITOSIS” Microtubules microtubule Kinetochore Microtubules microtubule Intact nuclear Fragments of nuclear Intact nuclear Fragments of envelope envelope envelope nuclear (b) Dinoflagellates (d) Most eukaryotes envelope Fragments of (d) Most eukaryotes Intact nuclear (b) Dinoflagellates nuclear PROTEINS envelope envelope (b) Dinoflagellates (d) Most eukaryotes LIPIDS  Mitosis Form of Cell Division in most eukaryotes: - DNA Replication – duplication & separation of the chromosome(s) - Cytokinesis – cytoplasmic events required to separate chromosomes & divide the cytoplasm - 1 cell gives rise to - 2 daughter cells with identical genetic complement - “preserves the continuity of life”  Cytoplasmic Events - Cytokinesis - Separation of the sister chromatids -> daughter chromosomes - Division of the cytoplasm - Nuclear envelope (membranes) dissolve & reform - Movement of daughter chromosomes away from each other (& fidelity therein) - Formation of new plasma membrane -> 2 daughter cells  Mitosis – The Mitotic Spindle - PROTEIN NETWORK: - Microtubule proteins– chromosomes move along - “CENTROSOME” PROTEIN COMPLEX – acts as anchor/nexus - Must be “POLARITY” – to result in 2 cells with equal chromosomal content…  Mitosis – CENTROSOME - Animal Cells - aka MTOC – Micro-Tubule Organizing Center - PROTEIN COMPLEX – basic protein unit “CENTRIOLE” - Normally 1 per cell - Before Cell Division (after DNA Rep/Chromosomal Duplication) => CENTROSOME DUPLICATION must also occur => 2 centrosomes per cell, allows division of Cytoplasm into 2  Mitosis – Spindle Formation Aster Centrosome Spindle microtubules - Microtubule proteins form from the CENTROSOME & extend into cytoplasm - More “Tubulin” protein subunits added on -> Expansion of the Microtubules - Short Microtubules – “Aster” - Longer Microtubules – “Spindle Microtubules” - TARGETS: Kinetochore proteins on the Chromosomal CENTROMERE  Video: Spindle Formation During Mitosis © 2018 Pearson Education Ltd.  Mitosis – Spindle Formation - Microtubules which bind a chromosome-> Kinetochore Microtubules - ASTERS @ 1 end & Microtubules at kinetochore -> PUSH/PULL - Places tortion/stress on sister chromatids/chromosomes  Mitosis – Separation - Enzyme assisted “Separase” – breaks down connections btw sister chromatids - Sister Chromatids migrate away - Moving along kinetochore microtubules – toward centriole, - Move along the network - Kinetochores M/T shorten – depolymerization, Chromatids move on as they do…  Cytokinesis – Division of Cytoplasm - Role of Spindle Microtubules regulating Division of Cytoplasm: - Opposing Centrosomes give “Polarity” - Short “Aster” microtubules give push in opposite direction – away from centre - Before separation, “Non-kinetochore microtubules” play important role; - > Elongating the cytoplasm by extending in opposing directions  Cytokinesis – “Cleavage” - Cleavage – division of cytoplasm - Division without growth, type of cleavage common in developing embryo - Formation of “Cleavage Furrow” - From which new membrane forms -> separating daughter cells  Cytokinesis – “Cleavage” Cleavage furrow Contractile ring of Daughter cells microfilaments - “Microfilament proteins” important here (actin & myosin) – - After separation & migration of chromosomes - New microfilament bundles form along center - ”Push” to counteract pull of Spindle…. - Invagination of membrane “Cleavage”  Cytokinesis – “Cleavage” - “Microfilament proteins” important here (actin & myosin) – - After separation & migration of chromosomes - New microfilament bundles form along center - ”Push” to counteract pull of Spindle…. - Invagination of membrane “Cleavage”  Stages of Mitosis - Frequency of mitosis is tightly regulated - & varies from cell-type/tissue/organism - Linked with Growth & Metabolism - Need new nucleotides for DNA Replication - New organelles, nutrients, increased cytoplasm, lipids… - Arranged into CELL CYCLE  Stages of Mitosis - Frequency of mitosis is tightly regulated - & varies from cell-type/organism - Linked with Growth & Metabolism - Need nucleotides from DNA Replication - New organelles, nutrients, increased cytoplasm, lipids… - Arranged into CELL CYCLE Mitosis – referred to as the M M-phase in cell cycle  Cell Cycle - Non Mitotic phase of cell – INTERPHASE - Divided into different parts: - G1 - S - G2 S G1 (DNA synthesis) G2  Stages of Cell Division (M-phase) - Cell Division involves – segregation of replicated chromosomes & Cytokinesis events - That need to be aligned - Temporal regulation - Divide mitosis into Phases - P - (P) - M - A - T  Stages of Cell Division (M-phase) - Cell Division involves – segregation of replicated chromosomes & Cytokinesis events - That need to be aligned - Temporal regulation - Divide mitosis into Phases - Prophase - Pro-Metaphase - Metaphase - Anaphase - Telophase  Stages of Cell Division (M-phase) Interphase - Preparatory events Growth G2 of Interphase Prophase Prom Centrosomes Chromosomes Early mitotic Fragments (with centriole (duplicated, Aster of nuclear spindle NUCLEUS: pairs) uncondensed) Centromere envelope DNA Replication CYTOPLASM: Centrosome duplication Plasma Nucleolus Two sister chromatids Kinetocho Nuclear membrane of one chromosome envelope  Stages of Cell Division (M-phase) Prophase 10 µm - NUCLEUS: G2 of Interphase Prophase Prometaphase Sister Chromatids Centrosomes appear Chromosomes Early mitotic Fragments Nonkinetochore (with centriole (duplicated, Aster of nuclear spindle microtubules pairs) uncondensed) Centromere envelope CYTOPLASM: Early Spindle formation Plasma Nucleolus Two sister chromatids Kinetochore Kinetochore Nuclear membrane of one chromosome microtubules envelope  Stages of Cell Division (M-phase) Pro-meta-phase 10 µm - phase NUCLEUS:Prophase Prometaphase Membrane Chromosomes Earlydissolves mitotic Fragments Nonkinetochore (duplicated, Aster of nuclear spindleremain) (Fragments microtubules uncondensed) Centromere envelope CYTOPLASM: Microtubules extend Attachment to Kinetochore Plasma Two sister chromatids Kinetochore Kinetochore r membrane of one chromosome microtubules pe  Stages of Cell Division (M-phase) Metaphase - “NUCLEUS”: Metaphase Anaphase Telophas Attached chromosomes Metaphase Cleavage align on “Metaphase Plate” plate furrow CYTOPLASM: Extension of Spindle forms symmetry & plate formation Daughter chromosomes Spindle Nuclear Centrosome at envelope one spindle pole forming  Stages of Cell Division (M-phase) 10 µm Anaphase - “NUCLEUS”: SeparationMetaphase of sister Anaphase Telophase and Cytokinesis chromatids Metaphase Cleavage Nucleolus plate furrow forming CYTOPLASM: De-polymerization of Microtubules & Migration of Chromatids Daughter chromosomes Spindle Nuclear Centrosome at envelope one spindle pole forming  Stages of Cell Division (M-phase) 10 µm Telophase - se “NUCLEUS”: Anaphase Telophase and Cytokinesis Reformation etaphase of nuclear Cleavage Nucleolus membrane plate (from remnants furrow forming of old envelope) CYTOPLASM: Cytokinesis & Cleavage Dissolution of Spindle Daughter chromosomes Nuclear Centrosome at envelope one spindle pole forming  Stages of Cell Division (M-phase) During G1 phase: Correct chromosome number 1 centrosomes 10 µm Telophase - S-phase: se “NUCLEUS”: Anaphase Telophase and Cytokinesis Double chromosome Reformation etaphase of nuclear Cleavage Nucleolus (chromatids) membrane plate (from remnants furrow forming G2-phase: of old envelope) 2 centrosomes CYTOPLASM: Cytokinesis & Cleavage Dissolution of Spindle Post-Mitosis (÷2) Daughter chromosomes Each daughter cell: Nuclear - Correct chromosome number Centrosome at envelope one spindle pole forming - 1 centrosome  VIDEO illustrating STAGES OF MITOSIS PLAY FROM 1:00 min to 3:00 min mark…  Regulation of the Cell Cycle - Frequency of mitosis is tightly regulated - & varies from cell-type/organism - Linked with Growth & Metabolism - Need nucleotides from DNA Replication - New organelles, nutrients, increased cytoplasm, lipids… - Arranged into CELL CYCLE Mitosis – referred to as the M M-phase in cell cycle  Regulation of the Cell Cycle G1 checkpoint Control G1 system S M G2 M checkpoint G2 checkpoint - Important to ensure enough metabolites available - SIGNALS in external (& internal) environment control this – Growth Factors - Too much PROLIFERATION – dangerous -> CANCER - Sometimes, a cell must die -> APOPTOSIS, “Programmed Cell Death” Regulation of the Cell Cycle G1 checkpoint Before DNA Replication Most important IF NO PROGRESSION SIGNAL -> Cell Cyle Arrest G0 phase Control G1 system S M G2 - Has the cell sufficient nutrients to allow DNA M checkpoint Replication & Cell G2 checkpoint Division Regulation of the Cell Cycle G1 checkpoint Control G1 system S M G2 Pre-mitosis check M checkpoint - DNA replication ok ? G2 checkpoint - DNA damage - 2 centrosomes?  Regulation of the Cell Cycle G1 checkpoint After Anaphase; To check for Control correct G1 system S separation of chromosomes, Preserve fidelity M G2 of DNA M checkpoint G2 checkpoint  require a surface for division EscapeDensity-dependent from Cellinhibition: Cycle Control cells form a single layer Density-dependent inhibition: cells divide to fill a gap and then stop 20 µm 20 µm (a) Normal mammalian cells (b) Cancer cells Cells will continue to grow if supplied with enough nutrients But reach tipping point – too many cells on monolayer -> Growth Inhibition (G1 checkpoint) Cancer Cells escape these checks & grow in unlimited manner (on top of each other) -> Masses aka Tumors  Functions of Cell Division a) Propagation of Life (a) Asexual reproduction b) Growth & embryonic development or organisms c) Repairs & Renewal after tissue damage (b) Growth and development (c) Tissue renewal  Functions of Cell Division a) Propagation of Life (a) Asexual reproduction b) Growth & embryonic development or organisms c) Repairs & Renewal after (b) Growth and tissue damage development d) Sexual Reproduction? - Variation in DNA allows evolution (c) Tissue renewal  Meiosis Interphase A special type of cell division that Pair of produces gametes – sperm & homologous egg cells chromosomes in diploid parent cell Halves the genetic complement Pair of duplicated Chromosomes homologous duplicate (chromosome content) chromosomes In diploids (2 copies of each Sister Diploid cell with chromosome) chromatids duplicated chromosomes => 1 copy of each chromosome Meiosis I (& linked genes) 1 Homologous chromosomes BASIS FOR INHERITANCE separate Haploid cells with 2 divisions; 1 cell -> 4 daughters duplicated chromosomes Meiosis II 1 REPLICATION with 2 Sister chromatids 2 SEPARATIONs separate In Round 1, pairs of chromosomes separate In Round 2, sister chromatids Haploid cells with unduplicated chromosomes separate (like mitosis)  Meiosis Basis for genetic variation: Prophase I Nonsister chromatids of meiosis held together during synapsis Before pairs of chromosomes Pair of separate, homologs 1 Synapsis and crossing over CROSSOVER occurs Chiasma - exchange of DNA 2 Movement to “HOMOLOGOUS the metaphase I RECOMBINATION” plate Centromere => Mutation TEM 3 Breakdown of Anaphase I proteins holding Division of chromosomes sister chromatid separates traits also – basis for arms together genetics & inheritance Anaphase II Random fertilization -> variation also Daughter cells Recombinant chromosomes  Recap Lecture 5 DNA Replication & Chromosomal Duplication Types of Cell Division Mitosis Cytoplasmic Events in Replication Stages of Cell Division & Regulation Special Forms of Cell Division (Meiosis)  FURTHER READING CAMPBELL BIOLOGY - Essential Biology Textbook - Ch 11/12 Notes on Blackboard Contact: [email protected] & Good Luck Links to Videos Used: https://www.pearson.com/channels/biology/asset/0a983823/bioflixto ur-of-an-animal-cell