Cell Cycle and Cell Division PDF

Cellular Division 1  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)...

Cellular Division 1  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) 2  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 3  DNA Replication DNA must be copied or replicated before cell Original DNA strand division Each new cell will then have an identical Two new, identical DNA copy of the DNA strands 4  Identical Daughter Cells Two identical daughter cells Parent Cell 5 Chromosomes 6  Prokaryotic Chromosome The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane 7  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 8  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 9  Compacting DNA into Chromosomes DNA is tightly coiled around proteins called histones 10  Chromosomes in Dividing Cells Duplicated chromosomes are called chromatids & are held together by the centromere Called Sister Chromatids 11  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 12  Boy or Girl? The Y Chromosome Decides Y - Chromosome X - Chromosome 13 Cell Reproduction 14  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 15 Cell Division in Prokaryotes 16  Cell Division in Prokaryotes  Prokaryotes such as bacteria divide into 2 identical cells by Parent cell the process of binary fission  Single chromosome makes a copy of itself Chromosome  Cell wall forms between the doubles chromosomes dividing the cell Cell splits 2 identical daughter cells 17 Prokaryotic Cell Undergoing Binary Fission 18 Animation of Binary Fission 19 The Cell Cycle 20  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 21 Cell Cycle 22  Interphase - G1 Stage 1st growth stage after cell division Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities 23  Interphase – S Stage Synthesis stage DNA is copied or replicated Two identical copies of DNA Original DNA 24  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 25 What’s Happening in Interphase? What the cell looks like Animal Cell What’s occurring 26  Sketch the Cell Cycle DNA Copied Cells prepare for Cells Division Mature Daughter Cells Cell Divides into Identical cells 27 Mitosis 28  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 29  Four Mitotic Stages Prophase Metaphase Anaphase Telophase 30  Early Prophase Chromatin in nucleus condenses to form visible chromosomes Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal) Nucleolus Cytoplasm Nuclear Membrane Chromosomes 31  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 32  Late Prophase Chromosomes Nucleus & Nucleolus have disintegrated 33  Spindle Fiber attached to Chromosome Kinetochore Fiber Chromosome 34  Review of Prophase What the cell looks like What’s happening 35  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 36 Sketch The Spindle 37  Metaphase Chromosomes, attached to the kinetochore fibers, move to the center of the cell Chromosomes are now lined up at the equator Equator of Cell Pole of the Cell 38  Metaphase Asters at the poles Spindle Fibers Chromosomes lined at the Equator 39  Metaphase Aster Chromosomes at Equator 40  Review of Metaphase What the cell looks like What’s occurring 41  Anaphase Occurs rapidly Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers 42  Anaphase Sister Chromatids being separated 43  Anaphase Review What the cell looks like What’s occurring 44  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 45 Comparison of Anaphase & Telophase 46  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 47  Cytokinesis Cleavage furrow in Cell plate in animal cell animal cell 48 Mitotic Stages 49  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) 50  Identical Daughter Cells What is the 2n or diploid number? 2 Chromosome number the same, but cells smaller than parent cell 51 Review of Mitosis 52 Draw & Learn these Stages 53 Draw & Learn these Stages 54  Name the Mitotic Stages: Interphase Name this? Telophase Prophase Name this? Metaphase Anaphase 55  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 Cytokinesis Telophase 56  Mitosis Animation Name each stage as you see it occur? 57 Mitosis in Onion Root Tips Do you see any stages of mitosis? 58 Test Yourself over Mitosis 59 Mitosis Quiz 60 Mitosis Quiz 61  Name the Stages of Mitosis: Early prophase Early Anaphase Metaphase Interphase Early Telophase, Begin cytokinesis Late Late telophase, Prophase Advanced cytokinesis Mid-Prophase Late Anaphase 62  Identify the Stages ? Early, Middle, & Late Prophase ? ? ? Late Prophase Metaphase Anaphase ? ? ? Late Anaphase Telophase Telophase & Cytokinesis 63 Locate the Four Mitotic Stages in Plants Anaphase Telophase Metaphase Prophase 64  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 65  Meiosis Formation of Gametes (Eggs & Sperm) 66  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) 67  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) 68  More Meiosis Facts  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 69  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 70 Fertilization – “Putting it all together” 2n = 6 1n =3 71  Replication of Chromosomes Replication is the process of duplicating a chromosome Occurs in Occurs prior to division Interphase Replicated copies are called sister chromatids Held together at centromere 72  A Replicated Chromosome Gene X Homologs Sister (same genes, different alleles) Chromatids (same genes, same alleles) Homologs separate in meiosis I and therefore different alleles separate. 73  Meiosis Forms Haploid Gametes  Meiosis must reduce the chromosome number by half  Fertilization then restores the 2n number from mom from dad child too much! meiosis reduces genetic content The right number! 74  Meiosis: Two Part Cell Division Sister chromatids Homologs separate separate Meiosis Meiosis I II Diploid Diploid Haploid 75  Meiosis I: Reduction Division Nucleus Spindle fibers Nuclear Early Prophase I envelope (Chromosome Late Metaphase I number doubled) Prophase I Anaphase I Telophase I (diploid) 76  Prophase I Early prophase Late prophase Homologs pair. Chromosomes condense. Crossing over occurs. Spindle forms. Nuclear envelope fragments. 77  Tetrads Form in Prophase I Homologous chromosomes Join to form a (each with sister chromatids) TETRAD Called Synapsis 78  Crossing-Over  Homologous chromosomes in a tetrad cross over each other  Pieces of chromosomes or genes are exchanged  Produces Genetic recombination in the offspring 79 Homologous Chromosomes During Crossing-Over 80  Crossing-Over Crossing-over multiplies the already huge number of different gamete types produced by independent assortment 81 Metaphase I Homologous pairs of chromosomes align along the equator of the cell 82  Anaphase I Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres. 83 Telophase I Nuclear envelopes reassemble. Spindle disappears. Cytokinesis divides cell into two. 84  Meiosis II Only one homolog of each chromosome Gene X is present in the cell. cell Sister chromatids carry identical genetic information. Meiosis II produces gametes with one copy of each chromosome and thus one copy of each gene. 85  Meiosis II: Reducing Chromosome Number Prophase II Metaphase II Telophase II Anaphase II 4 Identical haploid cells 86 Prophase II Nuclear envelope fragments. Spindle forms. 87 Metaphase II Chromosomes align along equator of cell. 88  Anaphase II Equator Pole Sister chromatids separate and move to opposite poles. 89 Telophase II Nuclear envelope assembles. Chromosomes decondense. Spindle disappears. Cytokinesis divides cell into two. 90 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 91 Gametogenesis Oogenesis or Spermatogenesis 92  Spermatogenesis Occurs in the testes Two divisions produce 4 spermatids Spermatids mature into sperm Men produce about 250,000,000 sperm per day 93 Spermatogenesis in the Testes Spermatid 94 Spermatogenesis 95  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 96 Oogenesis in the Ovaries 97  Oogenesis First polar body may divide a (haploid) X a Polar bodies X a die a X X Mitosis Meiosis I Meiosis II A X (if fertilization Oogonium occurs) A (diploid) Primary X oocyte A X Ovum (egg) (diploid) Mature Secondary A egg oocyte X (haploid) Second polar body (haploid) 98 Comparing Mitosis and Meiosis 99  Comparison of Divisions Mitosis Meiosis 2 Number of divisions 1 Number of daughter 2 4 cells Genetically identical? Yes No Chromosome # Same as parent Half of parent Where Somatic cells Germ cells When Throughout life At sexual maturity Role Growth and repair Sexual reproduction 100 101