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Chapter 9 Cellular Basis of Inheritance Brief Overview of Chapter • • • • • • 9.1 All Cells from Cells 9.2 The Cell Cycle 9.3 Mitosis (asexual) 9.4 Cancer Cells 9.5 Meiosis (sexual reproduction) 9.6 Genetic Variation Our Learning Goal Today 1. 2. Unicellular Vs Multicellular Reproduction Stages of the Cell Cycle 9.1 All Cells come from….Cells • Organisms reproduce their own kind – No humans with zebra babies or tigerman… • Cells are important for: – Repair, growth and reproduction • Reproduction • Asexual or Sexual – Asexual • Simple cell division with no genetic variation – Sexual • 2 parents involved, genetic material from each combine to produce genetically different offspring • Union of egg and sperm Reproduction • Unicellular Organism – Asexual usually; can sexually • Multicellular Organism – Sexually usually; some can asexually Which they “choose” depends on various reasons… anyone? 9.2 Cell Cycle • Body makes 25 million new cells per second! – Most of time spent doing cellular activities (not dividing) • 2 Phases of Cell Division – 1- Interphase • G1, S, G2 – 2- Mitotic Phase • Mitosis, Cytokinesis But First…. Chromo WHATS?! • Chromatin- fibers made up of DNA Forms Squiggly Where One half athey “X” of like join lines the shape in the chromosome inside center • Chromatid- one “side” of chromosome • Chromosomecondensed chromatin • Centromere- where 2 chromatids join The Cell Cycle • How often a cell divides depends on the type of cell • Eukaryotic cells that divide undergo cell cycle • Prokaryotic cells go through binary fission The Cell Cycle • Phase 1: Interphase – – – 90% cell life Routine function Metabolic functions 1. G1- First Growth – Is it healthy? 2. S- DNA copied – Copied correctly? 3. G2- Second Growth The Cell Cycle • Phase 2: Mitotic Phase – Cell divides 4. Mitosis: • Nucleus & duplicated chromosomes divide into 2 daughter nuclei 5. Cytokinesis • Cytoplasm divides Process produces 2 genetically identical daughter cells each with a single nucleus Mitosis unique to eukaryotes So… Did you LEARN Today?! 1. What are cells important for? 2. Describe how unicellular and multicellular cells reproduce. (how are they different) 3. Draw the Cell Cycle – Label each phase/step – Describe what’s happening in each – QUIZ 9.1/9.2/9.3 Thurs- CP BIOLOGY General Bio Cell Division (today’s notes) Mitosis • What’s happening? – Cells make identical copies – 4 steps • Why? 1. Prep for meiosis 2. Means of asexual reproduction R E M E M B E R… • Mitosis is PART of the Cell Cycle – Interphase • G1, S, G2 – Mitotic Phase •Mitosis, Cytokinesis These are the 4 steps to mitosis... Step 1: Prophase • Chromatin condenses into chromosomes • Nuclear envelope disappears • Spindles form (with microtubules) Step 2: Metaphase • Chromosomes gather across cell “equator” • Chromatids attaches to spindle microtubules Step 3: Anaphase • Sister chromatids pulled apart by microtubules toward poles • As they are pulled cell gets pushed out farther Step 4:Telophase • Spindles disappear • Nuclear envelopes appear around each nuclei • Chromosomes uncoil into chromatin Cytokinesis • Division of cytoplasm • Completes Cell Cycle – 2 genetically identical cells – Animals cytoplasm pinches – Plants cell plate forms Do you Remember? 1. What are the 2 phases of cell division? 2. What are the 5 steps to cell division and what phases are they found in? 3. What are the 4 steps of mitosis? 4. What is the purpose of mitosis? 5. How do prokaryotes reproduce? 6. What happens in each step of mitosis? 7. What is a pneumonic device to remember the steps of mitosis in order? Reinforcement Activity • Pages 186-187 MITOSIS FLIP BOOK!!! • Interphase • Prophase • Metaphase • Anaphase • Telophase – Label each on opposite sides!! 9.4 Cancer • Normal cells have “control system” – Malfunctions • Tumors & Cancer 9.4 Cancer • Out of control cell reproduction – Tumor (mass) • Benign tumors mass of normal cells • Malignant tumor mass of cancer cells – Cancer (disease) • Caused by severe disruption of mechanism that normally controls cell cycle 9.4 Cancer • Cancerous cells spread – Diseased cells replace normal ones (malignant) – If not killed, removed it spreads to other parts of the body and can form new tumors • Metastasis spread of cancer cells beyond their original site Cures? 9.4 Cancer Treatments • Malignant Vs Benign • Surgery? • Radiation Therapy (chemo) – Try to stop cell division – Anti-mitotic drugs… do what? • Side effects? 9.4 Cancer • Video Clips – Awake Tumor Removal – Angiogenisis 9.5 Meiosis • Each offspring in a sexually reproducing species inherits a unique combination of genes from its two parents – Creates a unique combination of traits 9.5 Meiosis • Meiosis cell division that produces 4 cells – Each with half the number of chromosomes as parent cell – Occurs in sex organs 9.5 Role of Chromosomes in Meiosis • Almost all cells have same number and type of chromosome within an organism – Males and Females from same species also have number and type • Humans have 46 chromosomes – Each has a twin (23 pairs) • Homologous chromosomes – Same sequences same inherited characteristics 9.5 Chromosome Role in Meiosis • Homologous chromosomes – Eye color gene • Same locations • Slightly different versions – (blue, brown, green) – DIFFERENT from sister chromatids! » Those are identical in every way 9.5 Chromosome Role in Meiosis • 23 homologous pairs of chromosomes (46 total) • PAGE 193 karyotype – Chromosome “map” – Females all 23 homologous pairs look alike – Males only 22; 1 pair look different • SEX CHROMOSOMES – Female XX – Male XY 9.5 Chromosome Role in Meiosis • Sex chromosomes – Determine if male or female – Most genes carried on “X” – X genes not on Y and vice versa 9.5 Chromosome Role in Meiosis • Have 2 sets of chromosomes (one from each parent)…key to life cycle – Diploid (2n) contain 2 homologous sets of chromosomes • Most cells are diploid • 2n=46 – Haploid (n) single set of homologous chromosomes • Sex cells (sperm, eggs) • n=23 • Formed through meiosis The birds and the bees… • Human Life Cycle – Nucleus of sperm (n) cell fuses with nucleus of egg (n) during fertilization – Egg & sperm = gametes – Forms human zygote (2n) • 2 sets of homologous chromosomes • Meiosis is the formation of these (n) Do You Remember? • • • • • • • • • Draw a benign and malignant tumor. Draw homologous chromosomes. What are the male and female sex chromosomes? How many pairs of chromosomes do humans have? What are the male and female gametes? What is a zygote? What symbol represents haploid? Diploid? What is a karyotype? The Process of Meiosis • Alternating diploid/haploid stages • w/o meiosis chromosome number would increase exponentially! • 2 Meiotic divisions – Meiosis I • Prophase I, Metaphase I, Anaphase I, Telophase I – Meiosis II • Prophase II, Metaphase II, Anaphase II, Telophase II The Process of Meiosis • Meiosis I – Prophase I • Homologous chromosomes stick lengthwise • Chromosomes form tetrads • Crossing over between tetrads One Big, One Little From each parent 9.5 Meiosis • Metaphase I – Tetrads move to middle of cell & line up across spindle 9.5 Meiosis • Anaphase I – Homologous chromosomes separate as they migrate to opposite poles of spindle – Sister chromatids move together – Only 2 chromosomes (w/2 copies) moving to each pole 9.5 Meiosis • Telophase I & Cytokinesis – Poles have haploid daughter nucleus – Nuclear envelope forms, cell divides 9.5 Meiosis • Prophase II – In each haploid daughter cell • Spindle attaches to centromeres & moves chromosomes to middle 9.5 Meiosis • Metaphase II – Chromosomes lined up in the middle with microtubules attached to each sister chromatid 9.5 Meiosis • Anaphase II – Sister chromatids separate & move to poles 9.5 Meiosis • Telophase II & Cytokinesis – Individual chromosomes at poles – Cytoplasm splits Final Product = 4 haploid daughter cells Review Game • Meiosis Memory!! • 6pm Appointments!! • Play against each other Meiosis • Illustrate Meiosis Prophase I: _______________________________ _______________________________ _______________________________ 1. Draw cell- use colored pencils 2. Label Pictures 3. Write out step to the right 4. Put in correct order Reflection Activity • Complete Venn Diagram for Mitosis & Meiosis – How are they similar? – Different: • What happens in mitosis but NOT in meiosis? • What happens in meiosis but NOT in mitosis? • What are the products