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Cell Division Slide 2 Rain Forest Rescue Hawaii rescue endangered species Slide 3 Goals promote reproduction produce more individuals Cyanea kuhihewa Kauai, Hawaii Slide 4 Sexual Vs. Asexual Reproduction Asexually 1 parent Genetic copy LM 340 Figure 8.1A lets split! Slide 5 Sexually Variety Figure 8.1B Sexual Vs. Asexual Reproduction Slide 6 The Cycle of Life Fertilization of gametes Cell division and growth Production of gametes Death Slide 7 Cell Reproduction Parent cells split New cells provide daughter cells with everything! Clones! Slide 8 Division Mechanisms Prokaryotic organisms Fission Eukaryotic organisms Mitosis Meiosis Slide 9 Prokaryotic Equal size High mutation rate Colorized TEM 32,500 Prokaryotic chromosomes Figure 8.3B Binary Fission Slide 10 Prokaryotic chromosome Plasma membrane Cell wall Duplication of chromosome and separation of copies 1 Continued elongation of the cell and movement of copies 2 Division into two daughter cells 3 Figure 8.3A Binary Fission Slide 11 Mitosis Used for: Growth Cell replacement Asexual reproduction Slide 12 Meiosis Used for: Sexual reproduction Slide 13 LM 600 DNA w/ proteins Only present during cell division Form from chromatin fibers Figure 8.4A Chromosomes Slide 14 DNA and proteins arranged as cylindrical fiber DNA histone one nucleosome Figure 9.2 Page 153 Slide 15 Sister Chromatids Replicates Before division Joined at centromere TEM 36,000 Centromere Sister chromatids Figure 8.4B Chromosomes Slide 16 Sister Chromatids Separation daughter cells Complete set Centromere Chromosome duplication Sister chromatids Chromosome distribution to daughter cells Figure 8.4C Chromosomes Slide 17 Chromosome # = # of chromosomes Somatic cells Diploid (2n) Two of each (XX) Gametes Haploid (1n) One of each (X) Slide 18 Chromosomes Diploid # (n) = 46 Two sets of 23 One set inherited from ______ and the other from ________ Slide 19 mitosis, cytoplasmic division chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in cell at interphase same chromosome (duplicated) in interphase prior to mitosis Slide 20 The Cell Cycle Phases Interphase Mitosis Slide 21 The Cell Cycle G1 S G2 Mitosis telophase anaphase metaphase prophase interphase Slide 22 The Cell Cycle Interphase Longest 3 Phases G1: growth S phase: DNA copied G2: readied for division Slide 23 The Cell Cycle Mitosis Nuclear division Usually followed by cytoplasmic division Four stages Slide 24 Mitosis Early Prophase Chromosomes begin to condense Figure 9.7 Page 156 Slide 25 Mitosis Late Prophase Microtubules are assembled Centriole moved to opposite pole Nuclear envelope breaks up Figure 9.7 Page 156 Slide 26 Mitosis Spindle forms Attach to sister chromatids Figure 9.7 Page 156 Transition to Metaphase Slide 27 Mitosis Metaphase Chromosomes at equator Figure 9.7 Page 156 Slide 28 Mitosis Anaphase Sister chromatids pulled apart Figure 9.7 Page 156 Slide 29 Mitosis Telophase Chromosomes spread Nuclear enevelopes form Figure 9.7 Page 156 Slide 30 Results of Mitosis Two daughter nuclei Figure 9.7 Page 156 Slide 31 Cytoplasmic Division Two mechanisms Cell plate formation (plants) Cleavage (animals) Slide 32 Cell Plate Formation Slide 33 Animal Cell Division Figure 9.9 Page 159 Slide 34 Stopping the Cycle Normally stop in interphase Neurons Ways to stop the cell cycle Anchorage dependence Density-dependent inhibition Growth factors Slide 35 Critical checkpoints Control system G1G1 S G2G2 M G 1 checkpoint G 2 checkpoint M checkpoint G0G0 Figure 8.9A Stopping the Cycle Slide 36 Control system G1G1 S G2G2 M G 1 checkpoint Plasma membrane Growth factor Receptor protein Relay proteins Signal transduction pathway Figure 8.9B Growth Factors Slide 37 Cancer Uncontrolled cell division form masses Radiation and chemotherapy Malignant tumors Slide 38 Tumor Glandular tissue A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body. Lymph vessels Blood vessel Figure 8.10 Slide 39 Growth LM 500 Figure 8.11A What was mitosis for? Slide 40 LM 700 Cell replacement Figure 8.11B Slide 41 Asexual reproduction LM 10 Figure 8.11C Slide 42 Sexual Reproduction Involves Meiosis Gamete production Fertilization Genetic variation! Slide 43 Homologous Pairs Set of matched chromosomes Carry genes Locus Chromosomes Centromere Sister chromatids Sexual Reproduction Slide 44 Homologous pairs Same genes, different alleles Paternal and maternal chromosomes Slide 45 Sexual Reproduction Life stages Diploid stages Haploid stages Gametes ALWAYS haploid Zygote ALWAYS diploid Slide 46 Mitosis and development Multicellular diploid adults (2n = 46) Diploid zygote (2n = 46) 2n2n Meiosis Fertilization Egg cell Sperm cell n Haploid gametes (n = 23) n Slide 47 Sexual Reproduction Shuffles alleles Offspring inherit new combos Increases variation Variation is the basis for evolutionary change Slide 48 Sexual Reproduction Chromosome # Stomatic cells = ?n Gametes = ?n Meiosis halves chromosome number Slide 49 Meiosis: Two Divisions Two consecutive nuclear divisions Meiosis I Meiosis II DNA is not duplicated between divisions Four haploid nuclei form Slide 50 Meiosis I Each homologue in the cell pairs with its partner, then the partners separate In-text figure Page 165 Homologous pairs split Slide 51 Meiosis II Sister chromatids split one chromosome (duplicated) two chromosomes (unduplicated) Slide 52 Meiosis I - Stages Prophase IMetaphase IAnaphase ITelophase I Slide 53 Meiosis I Prophase I Chromosome pairs with homologue Crossing-over occurs Slide 54 Meiosis I Figure 10.4 Page 167 Metaphase I Slide 55 Meiosis I Anaphase I Homologous pairs separate The sisters? Figure 10.4 Page 167 Slide 56 Meiosis I Telophase I Cytoplasmic division Figure 10.4 Page 167 Slide 57 Meiosis II Stages Slide 58 Meiosis II Prophase II Slide 59 Meiosis II Metaphase II Slide 60 Meiosis II Anaphase II Sister chromatids separate Slide 61 Meiosis II Telophase II Four haploid cells Figure 10.4 Page 167 Slide 62 Variation? Independent orientation (assortment) Random grab by microtubules Position of M and P chromosomes at equator random Either pair can end up at either poll! Slide 63 Variation? Combination 1 Combination 2 Combination 3 Combination 4 Gametes Metaphase II Two equally probable arrangements of chromosomes at metaphase I Possibility 1Possibility 2 Slide 64 Variation? The # of possible combinations of chromosomes in a gamete is: 2 n (n is the haploid #) 2 23 = 8 Trillion How many combinations for a zygote? Slide 65 Crossing Over Shuffles alles Genetic recombination Tetrad in parent cell (homologous pair of duplicated chromosomes) ec EC White Pink ec ec EC EC Meiosis BlackBrown Chromosomes of the four gametes Eye-color genes Coat-color genes Brown coat (C); black eyes (E) White coat (C); pink eyes (e) Figure 8.17A Figure 8.17B Variatoin? Slide 66 Figure 8.18A Chiasma Tetrad Centromere TEM 2,200 Variation? Slide 67 Coat-color genes Eye-color genes Tetrad (homologous pair of chromosomes in synapsis) C E c e C E c e C E c e Chiasma C E C e c E c e C E C e c E c e Parental type of chromosome Recombinant chromosome Parental type of chromosome Gametes of four genetic types How? Nonsister chromosomes exchange segments recombine maternal and paternal segments Breakage of homologous chromatids 1 Joining of homologous chromatids 2 3 Separation of homologous chromosomes at anaphase I 4 Separation of chromatids at anaphase II and completion of meiosis Figure 8.18B Slide 68 Variation? Can you come up with 3 sources of variation? Slide 69 Changes in Chromosome # Accidents during meiosis Nondisjunction Of homologous pairs Of sister chromatids Variation? Slide 70 Nondisjunction in meiosis I Normal meiosis II Gametes n 1 n 1 Number of chromosomes Nondisjunction in meiosis II Normal meiosis I Gametes n 1n 1 n n Number of chromosomes Figure 8.21A Figure 8.21B Slide 71 Sperm cell Egg cell n (normal) n + 1 Zygote 2n + 1 Figure 8.21C Slide 72 Blood culture Fluid Centrifuge Packed red and white blood cells Hypotonic solution Fixative White blood cells Stain Centromere Pair of homologous chromosomes Sister chromosomes 2,600X A blood culture is centrifuged to separate the blood cells from the culture fluid. 1 The fluid is discarded, and a hypotonic solution is mixed with the cells. This makes the red blood cells burst. The white blood cells swell but do not burst, and their chromosomes spread out. 2 Another centrifugation step separates the swollen white blood cells. The fluid containing the remnants of the red blood cells is poured off. A fixative (preservative) is mixed with the white blood cells. A drop of the cell suspension is spread on a microscope slide, dried, and stained. 3 The slide is viewed with a microscope equipped with a digital camera. A photograph of the chromosomes is entered into a computer, which electronically arranges them by size and shape. 4 The resulting display is the karyotype. The 46 chromosomes here include 22 pair of autosomes and 2 sex chromosomes, X and Y. Although difficult to discern in the karyotype, each of the chromosomes consists of two sister chromatids lying very close together (see diagram). 5 Figure 8.19 Slide 73 Slide 74 Down syndrome - by trisomy of 21 5,000 Figure 8.20AFigure 8.20B Variation? Slide 75 Chance of Down syndrome Age of mother 45 5035 3025 40 20 90 0 10 20 30 40 50 60 70 80 Infants with Down syndrome (per 1,000 births) Figure 8.20C Slide 76 Variation? Changes in Sex Chromosomes Figure 8.22A Poor beard growth Breast Development Under-developed testes Figure 8.22B Characteristic facial features Web of skin Constriction of aorta Poor breast development Under developed ovaries Slide 77 Human sex chromosome abnormalities Slide 78 Question of the Day 2x The cancer drug called paclitaxel (Taxol) interferes with microtubule formation. 1) How? 2) Why is this effective and against what types of cancer? 3) What plant is this drug made from?