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Premium member Presentation Transcript Cellular Division : 1 Cellular Division Cell Division : 2 Cell Division All cells are derived from pre-existing cells New cells are produced for growth and to replace damaged or old cells Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals) Keeping Cells Identical : 3 Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules DNA Replication : 4 DNA Replication DNA must be copied or replicated before cell division Each new cell will then have an identical copy of the DNA Original DNA strand Two new, identical DNA strands Identical Daughter Cells : 5 Identical Daughter Cells Parent Cell Two identical daughter cells Chromosomes : 6 Chromosomes Prokaryotic Chromosome : 7 Prokaryotic Chromosome The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane Eukaryotic Chromosomes : 8 Eukaryotic Chromosomes All eukaryotic cells store genetic information in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells Human body cells have 46 chromosomes or 23 identical pairs Eukaryotic Chromosomes : 9 Eukaryotic Chromosomes Each chromosome is composed of a single, tightly coiled DNA molecule Chromosomes can’t be seen when cells aren’t dividing and are called chromatin Compacting DNA into Chromosomes : 10 Compacting DNA into Chromosomes DNA is tightly coiled around proteins called histones Chromosomes in Dividing Cells : 11 Chromosomes in Dividing Cells Duplicated chromosomes are called chromatids & are held together by the centromere Called Sister Chromatids Karyotype : 12 Karyotype A picture of the chromosomes from a human cell arranged in pairs by size First 22 pairs are called autosomes Last pair are the sex chromosomes XX female or XY male Boy or Girl? : 13 Boy or Girl? Y - Chromosome X - Chromosome The Y Chromosome Decides Cell Reproduction : 14 Cell Reproduction Types of Cell Reproduction : 15 Types of Cell Reproduction Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Mitosis & binary fission are examples of asexual reproduction Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Meiosis is an example Cell Division in Prokaryotes : 16 Cell Division in Prokaryotes Cell Division in Prokaryotes : 17 Cell Division in Prokaryotes Prokaryotes such as bacteria divide into 2 identical cells by the process of binary fission Single chromosome makes a copy of itself Cell wall forms between the chromosomes dividing the cell Parent cell 2 identical daughter cells Chromosome doubles Cell splits Prokaryotic Cell Undergoing Binary Fission : 18 Prokaryotic Cell Undergoing Binary Fission Animation of Binary Fission : 19 Animation of Binary Fission The Cell Cycle : 20 The Cell Cycle Five Phases of the Cell Cycle : 21 Five Phases of the Cell Cycle G1 - primary growth phase S – synthesis; DNA replicated G2 - secondary growth phase collectively these 3 stages are called interphase M - mitosis C - cytokinesis Cell Cycle : 22 Cell Cycle Interphase - G1 Stage : 23 Interphase - G1 Stage 1st growth stage after cell division Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities Interphase – S Stage : 24 Interphase – S Stage Synthesis stage DNA is copied or replicated Two identical copies of DNA Original DNA Interphase – G2 Stage : 25 Interphase – G2 Stage 2nd Growth Stage Occurs after DNA has been copied All cell structures needed for division are made (e.g. centrioles) Both organelles & proteins are synthesized What’s Happening in Interphase? : 26 What’s Happening in Interphase? What the cell looks like Animal Cell What’s occurring Sketch the Cell Cycle : 27 Sketch the Cell Cycle Daughter Cells DNA Copied Cells Mature Cells prepare for Division Cell Divides into Identical cells Mitosis : 28 Mitosis Mitosis : 29 Mitosis Division of the nucleus Also called karyokinesis Only occurs in eukaryotes Has four stages Doesn’t occur in some cells such as brain cells Four Mitotic Stages : 30 Four Mitotic Stages Prophase Metaphase Anaphase Telophase Early Prophase : 31 Early Prophase Chromatin in nucleus condenses to form visible chromosomes Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal) Chromosomes Nucleolus Cytoplasm Nuclear Membrane Late Prophase : 32 Late Prophase Nuclear membrane & nucleolus are broken down Chromosomes continue condensing & are clearly visible Spindle fibers called kinetochores attach to the centromere of each chromosome Spindle finishes forming between the poles of the cell Late Prophase : 33 Late Prophase Nucleus & Nucleolus have disintegrated Chromosomes Spindle Fiber attached to Chromosome : 34 Spindle Fiber attached to Chromosome Kinetochore Fiber Chromosome Review of Prophase : 35 Review of Prophase What the cell looks like What’s happening Spindle Fibers : 36 Spindle Fibers The mitotic spindle form from the microtubules in plants and centrioles in animal cells Polar fibers extend from one pole of the cell to the opposite pole Kinetochore fibers extend from the pole to the centromere of the chromosome to which they attach Asters are short fibers radiating from centrioles Sketch The Spindle : 37 Sketch The Spindle Metaphase : 38 Metaphase Chromosomes, attached to the kinetochore fibers, move to the center of the cell Chromosomes are now lined up at the equator Pole of the Cell Equator of Cell Metaphase : 39 Metaphase Chromosomes lined at the Equator Asters at the poles Spindle Fibers Metaphase : 40 Metaphase Aster Chromosomes at Equator Review of Metaphase : 41 Review of Metaphase What the cell looks like What’s occurring Anaphase : 42 Anaphase Occurs rapidly Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers Anaphase : 43 Anaphase Sister Chromatids being separated Anaphase Review : 44 Anaphase Review What the cell looks like What’s occurring Telophase : 45 Telophase Sister chromatids at opposite poles Spindle disassembles Nuclear envelope forms around each set of sister chromatids Nucleolus reappears CYTOKINESIS occurs Chromosomes reappear as chromatin Comparison of Anaphase & Telophase : 46 Comparison of Anaphase & Telophase Cytokinesis : 47 Cytokinesis Means division of the cytoplasm Division of cell into two, identical halves called daughter cells In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell Cytokinesis : 48 Cytokinesis Cleavage furrow in animal cell Cell plate in animal cell Mitotic Stages : 49 Mitotic Stages Daughter Cells of Mitosis : 50 Daughter Cells of Mitosis Have the same number of chromosomes as each other and as the parent cell from which they were formed Identical to each other, but smaller than parent cell Must grow in size to become mature cells (G1 of Interphase) Identical Daughter Cells : 51 Identical Daughter Cells Chromosome number the same, but cells smaller than parent cell What is the 2n or diploid number? 2 Review of Mitosis : 52 Review of Mitosis Draw & Learn these Stages : 53 Draw & Learn these Stages Draw & Learn these Stages : 54 Draw & Learn these Stages Name the Mitotic Stages: : 55 Interphase Prophase Metaphase Anaphase Telophase Name the Mitotic Stages: Name this? Name this? Eukaryotic Cell Division : 56 Eukaryotic Cell Division Used for growth and repair Produce two new cells identical to the original cell Cells are diploid (2n) Chromosomes during Metaphase of mitosis Prophase Metaphase Anaphase Telophase Cytokinesis Mitosis Animation : 57 Mitosis Animation Name each stage as you see it occur? Mitosis in Onion Root Tips : 58 Mitosis in Onion Root Tips Do you see any stages of mitosis? Test Yourself over Mitosis : 59 Test Yourself over Mitosis Mitosis Quiz : 60 Mitosis Quiz Mitosis Quiz : 61 Mitosis Quiz Name the Stages of Mitosis: : 62 Name the Stages of Mitosis: Interphase Early prophase Mid-Prophase Late Prophase Metaphase Late Anaphase Early Anaphase Early Telophase, Begin cytokinesis Late telophase, Advanced cytokinesis Identify the Stages : 63 Identify the Stages Early, Middle, & Late Prophase Late Prophase Metaphase Anaphase Late Anaphase Telophase Telophase & Cytokinesis ? ? ? ? ? ? ? Locate the Four Mitotic Stages in Plants : 64 Locate the Four Mitotic Stages in Plants Metaphase Prophase Anaphase Telophase Uncontrolled Mitosis : 65 Uncontrolled Mitosis If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors Oncogenes are special proteins that increase the chance that a normal cell develops into a tumor cell Cancer cells MeiosisFormation of Gametes (Eggs & Sperm) : 66 MeiosisFormation of Gametes (Eggs & Sperm) Facts About Meiosis : 67 Facts About Meiosis Preceded by interphase which includes chromosome replication Two meiotic divisions --- Meiosis I and Meiosis II Called Reduction- division Original cell is diploid (2n) Four daughter cells produced that are monoploid (1n) Facts About Meiosis : 68 Facts About Meiosis Daughter cells contain half the number of chromosomes as the original cell Produces gametes (eggs & sperm) Occurs in the testes in males (Spermatogenesis) Occurs in the ovaries in females (Oogenesis) More Meiosis Facts : 69 Start with 46 double stranded chromosomes (2n) After 1 division - 23 double stranded chromosomes (n) After 2nd division - 23 single stranded chromosomes (n) Occurs in our germ cells that produce gametes More Meiosis Facts Why Do we Need Meiosis? : 70 Why Do we Need Meiosis? It is the fundamental basis of sexual reproduction Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote Fertilization – “Putting it all together” : 71 Fertilization – “Putting it all together” 1n =3 2n = 6 Replication of Chromosomes : 72 Replication of Chromosomes Replication is the process of duplicating a chromosome Occurs prior to division Replicated copies are called sister chromatids Held together at centromere Occurs in Interphase A Replicated Chromosome : 73 A Replicated Chromosome Gene X Homologs separate in meiosis I and therefore different alleles separate. Meiosis Forms Haploid Gametes : 74 Meiosis Forms Haploid Gametes Meiosis must reduce the chromosome number by half Fertilization then restores the 2n number The right number! Meiosis: Two Part Cell Division : 75 Meiosis: Two Part Cell Division Homologs separate Sister chromatids separate Diploid Diploid Haploid Meiosis I: Reduction Division : 76 Meiosis I: Reduction Division Early Prophase I (Chromosome number doubled) Late Prophase I Metaphase I Anaphase I Telophase I (diploid) Prophase I : 77 Prophase I Early prophase Homologs pair. Crossing over occurs. Late prophase Chromosomes condense. Spindle forms. Nuclear envelope fragments. Tetrads Form in Prophase I : 78 Tetrads Form in Prophase I Homologous chromosomes(each with sister chromatids) Join to form a TETRAD Called Synapsis Crossing-Over : 79 Crossing-Over Homologous chromosomes in a tetrad cross over each other Pieces of chromosomes or genes are exchanged Produces Genetic recombination in the offspring Homologous Chromosomes During Crossing-Over : 80 Homologous Chromosomes During Crossing-Over Crossing-Over : 81 Crossing-over multiplies the already huge number of different gamete types produced by independent assortment Crossing-Over Metaphase I : 82 Metaphase I Homologous pairs of chromosomes align along the equator of the cell Anaphase I : 83 Anaphase I Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres. Telophase I : 84 Telophase I Nuclear envelopes reassemble. Spindle disappears. Cytokinesis divides cell into two. Meiosis II : 85 Meiosis II Only one homolog of each chromosome is present in the cell. Gene X Meiosis II: Reducing Chromosome Number : 86 Meiosis II: Reducing Chromosome Number Prophase II Metaphase II Anaphase II Telophase II 4 Identical haploid cells Prophase II : 87 Prophase II Nuclear envelope fragments. Spindle forms. Metaphase II : 88 Metaphase II Chromosomes align along equator of cell. Anaphase II : 89 Anaphase II Sister chromatids separate and move to opposite poles. Equator Pole Telophase II : 90 Telophase II Nuclear envelope assembles. Chromosomes decondense. Spindle disappears. Cytokinesis divides cell into two. Results of Meiosis : 91 Results of Meiosis Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome One allele of each gene Different combinations of alleles for different genes along the chromosome Gametogenesis : 92 Gametogenesis Oogenesis or Spermatogenesis Spermatogenesis : 93 Spermatogenesis Occurs in the testes Two divisions produce 4 spermatids Spermatids mature into sperm Men produce about 250,000,000 sperm per day Spermatogenesis in the Testes : 94 Spermatogenesis in the Testes Spermatid Spermatogenesis : 95 Spermatogenesis Oogenesis : 96 Oogenesis Occurs in the ovaries Two divisions produce 3 polar bodies that die and 1 egg Polar bodies die because of unequal division of cytoplasm Immature egg called oocyte Starting at puberty, one oocyte matures into an ovum (egg) every 28 days Oogenesis in the Ovaries : 97 Oogenesis in the Ovaries Oogenesis : 98 Oogenesis Comparing Mitosis and Meiosis : 99 Comparing Mitosis and Meiosis Comparison of Divisions : 100 Comparison of Divisions Slide 101: 101 You do not have the permission to view this presentation. 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