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Mitosis and Meiosis Chapter 12 & 13 Mitosis & Meiosis.

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1 Mitosis and Meiosis Chapter 12 & 13 Mitosis & Meiosis

2 Next Unit: Genetics & DNA Chapter 12 & 13: Mitosis & Meiosis Chapter 14: Principles of Heredity Chapter 15: Human Genetics & Disorders Chapter 16: DNA: History, Structure & Function **Three Labs will be done for this Unit Goal: to complete before Thanksgiving and to take Test #3 on 11/20 (Tuesday)

3 Video #1: Generations-Mitosis & Meiosis 1.In the mid 1800s what did Paseur, Lister do? In 1876, What did Walter Flemming do that provided better visualization of parts in the cell? What did he see & discover? 2.Chromosomes literally mean: _______ 3.What is a centromere and what is its function? 4.What is a karyotype and what does it reveal? What are homologous chromosomes? 5.How many chromosomes do humans, fruit flies (Drosophila), horsetails, Toads, and pea plants have? 6.Name the business used in the 2 nd segment to show the importance of mitosis. 7.Briefly explain what grafting is? 8.A complete cycle can be completed in about ______hrs in a rapidly dividing tissue such as bone marrow. During this time mitosis occurs for only _______ hr(s). Pg Name the FOUR phases of Mitosis and two key events that occur. (See pg ) 10.Name two differences between Mitosis & Meiosis after watching the final segment. ****Write the Title for each segment and THREE key statements for each segment.

4 Introductory Questions #1 1) How much DNA does a typical human cell have? How are chromosomes differ from chromatin? 2) How is a somatic cell different from a gamete? 3) How is every species different in regards to their chromosomes? 4) Name the main stages of the cell cycle. (pg. 221) 5) What are the four stages of mitosis? Which stage is the longest and which stage is the shortest? 6) Give three specific events that occur during prophase. 7) How are plant cell different from animal cells when they divide?

5 Mitosis Occurs only in certain types of cells Form of asexual reproduction Produces two genetically identical cells from one cell. The splitting or dividing of the nucleus Viewed in different stages by examining chromosome formation and behavior.

6 Significance of Understanding Mitosis Preserves the continuity of life Allows organisms to grow, repair, and reproduce Important in unlocking the mysteries of embryonic development & stem cells Important in understanding how cancer develops and could someday provide clues in stopping cancer.

7 Cell replacement (seen here in skin) Dead cells Figure 8.11B Dividing cells Epidermis, the outer layer of the skin Dermis

8 Packaging of Genetic Material Structure / Activity Diameter DNA: smallest structure about (2 nm) DNA & Histones = Nucleosome (10 nm) Chromatin Fibers** (30 nm) Extensive Looping (300 nm) Further Condensing (700 nm) Fully Formed Chromosome (1400 nm)

9 Chromosomes Condensed DNA attached to proteins Can only be seen when a cell is actively undergoing mitosis. Typical humans form 46 chromosomes vs. other organisms which varies significantly. Our 46 chromosomes are thought to contain anywhere from 25,000 to 100,000 genes. Duplicated before mitosis occurs producing a sister chromatid (identical copy) Sister chromatids held together by Centromere

10 When the cell cycle operates normally, mitotic cell division functions in: –Growth (seen here in an onion root) Cells from an onion Root tip Figure 8.11A

11 E. coli dividing Figure 8.3x

12 Asexual reproduction (seen here in a hydra) Figure 8.11C

13 A eukaryotic cell has many more genes than a prokaryotic cell –The genes are grouped into multiple chromosomes, found in the nucleus –The chromosomes of this plant cell are stained dark purple THE EUKARYOTIC CELL CYCLE AND MITOSIS Figure 8.4A

14 Human male bands Figure 8.19x3

15 Human female karyotype Figure 8.19x2

16 Before a cell starts dividing, the chromosomes are duplicated –This process produces sister chromatids Centromere Sister chromatids Figure 8.4B

17 When the cell divides, the sister chromatids separate –Two daughter cells are produced –Each has a complete and identical set of chromosomes Centromere Sister chromatids Figure 8.4C Chromosome duplication Chromosome distribution to daughter cells


19 METAPHASETELOPHASE AND CYTOKINESIS Metaphase plate SpindleDaughter chromosomes Cleavage furrow Nucleolus forming Nuclear envelope forming ANAPHASE Figure 8.6 (continued)

20 The Cell Cycle: Generation Time Interphase: most of a cells life (90%) -G1: 1 st gap of growth -S phase: DNA is duplicated (synthesized) -G2 phase: 2 nd gap of growth Mitosis : splitting of the nucleus (PMAT) Cytokinesis : separation of the cytoplasm

21 The cell cycle consists of two major phases: –Interphase, where chromosomes duplicate and cell parts are made –The mitotic phase, when cell division occurs The cell cycle multiplies cells Figure 8.5

22 Interphase

23 Cells spend most of its time in this phase Cells are growing DNA has to be replicated (all 2 meters of it) Proteins are being produced 90% of all cells are in this phase Three phases:G 1, S, and G 2

24 Prophase

25 Chromatin thickens (coils) into chromosomes Two copies of DNA are present: sister chromatids (twice the amount of DNA is present) Centrioles replicate forming another centrosome separate. Centrioles separate to each side of the nucleus Nuclear membrane (envelope) disappears Microtubules elongate forming the spindle apparatus

26 Metaphase

27 Chromosomes align themselves up in the center of the cell Spindle fibers (microtubules) attach to the centromere of the chromosomes Longest phase of Mitosis

28 Metaphase

29 Mitotic spindle Figure 8.6x2

30 Anaphase - Early & Late

31 Anaphase Chromosomes separate by the shortening of the microtubules. The sister chromatids separate to each side (pole) of the cell. (humans: 46 to each side) The centrosome is located at each side of the cell.

32 Telophase (Plant & Animal)

33 Cytokinesis: Plant vs Animal Cells Cleavage furrow: animals cells Cell plate: Plant cells

34 In animals, cytokinesis occurs by cleavage –This process pinches the cell apart Cytokinesis differs for plant and animal cells Figure 8.7A Cleavage furrow Contracting ring of microfilaments Daughter cells

35 In plants, a membranous cell plate splits the cell in two Vesicles containing cell wall material Cell plate forming Figure 8.7B Cell plateDaughter cells Wall of parent cell Daughter nucleus Cell wallNew cell wall

36 When the cell cycle operates normally, mitotic cell division functions in: –Growth (seen here in an onion root) Cells from an onion Root tip Figure 8.11A

37 Mitosis collage, light micrographs Figure 8.6x1

38 Whitefish-phases of Mitosis

39 Various phases of Mitosis-Plants

40 Which Phase is this?

41 Sea urchin development Figure 8.0x

42 Cell cycle collage Figure 8.5x

43 Fibroblast growth Figure 8.8x

44 Total Class Data for all Three Classes: Fall 2005

45 Total Class Data for all Three Classes: Fall 2006

46 Regulation of Cell Division Driven by specific molecular signals Research has shown: –Two cells in different phases causes the other to be pushed into the next phases. –Ex. S phase & G 1 grown together will cause the G 1 cell to enter into the S phase immediately M phase cell & G 1 cell will cause the G 1 cell to enter into the M phase immediately. There is an obvious control system in place.

47 Regulating Mitosis-Control System (pg ) Most cells can divide up to 50 times Control of the Cell cycle involves three checkpoints -G 1 (most important checkpoint) = restriction point (G 0 : non-dividing state) -G 2 -M phase Growth factors (proteins): Cyclins & Kinases –Kinases: phosphorylate proteins, gives the go ahead –Cdk: are kinases that must be attached to a cyclin to be activated –MPF: Maturation promoting factor (Fig: pg. 230) Complex of kinase and cyclin Triggers the passage from G 2 phase into M phase peaks during Metaphase

48 Proteins within the cell control the cell cycle –Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide Growth factors signal the cell cycle control system G 1 checkpoint M checkpoint G 2 checkpoint Control system Figure 8.9A

49 Cyclin & Kinase effects on the cell cycle. Animated link: edicine/2001/cellcycle.html edicine/2001/cellcycle.html

50 Introductory Questions #2 1)Which checkpoint in the regulation of mitosis is considered the restriction point? Why point and not the others? 2)Name the two protein molecules that are high in concentration during the mitotic (M) phase of the cell cycle. Name the complex that it forms. 3)Why are telomeres considered to be a mitotic clock? 4)How are tumor supressor genes different from an oncogene? What is the difference between a malignant tumor and a benign tumor? 5)When looking at the hypothetical sequence of how mitosis may have evolved how is the process different in a bacteria and diatom from a plant and animal cell?

51 Cyclin & MPF Concentrations

52 Growth Factors that stimulate Cell Division PDGF: Platelet-derived growth factor causes fibroblasts to divide in response to an injury. Has been shown to be effective in artificial conditions Cytokinins: key hormone in plants that promotes cell division

53 The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell division Growth factor Figure 8.8B Cell cycle control system Plasma membrane Receptor protein Signal transduction pathway G 1 checkpoint Relay proteins

54 Mitotic Clock Mechanisms in Cells Telomeres, Proteins, Cell size (SA), hormones, & Growth factors Telomeres: Segments of DNA (200 repeated sequences of nucleotides) are lost at the tips of the chromosomes with each mitotic event. –(Mitotic clock) the tips of chromosomes wear down and lose DNA sequences over time. –Six Nucleotide sequence repeated hundreds of times –1,200 nucleotides are removed after each mitotic event

55 Image of Telomeres-notice light Blue Regions

56 Chromosomes in green & Telomeres in yellow

57 Most animal cells divide only when stimulated, and others not at all In laboratory cultures, most normal cells divide only when attached to a surface –They are anchorage dependent Anchorage, cell density, and chemical growth factors affect cell division

58 Cells continue dividing until they touch one another –This is called density-dependent inhibition Cells anchor to dish surface and divide. Figure 8.8A When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).

59 Growth factors are proteins secreted by cells that stimulate other cells to divide After forming a single layer, cells have stopped dividing. Figure 8.8B Providing an additional supply of growth factors stimulates further cell division. See pg. 232

60 Malignant tumors can invade other tissues and may kill the organism Tumor Figure 8.10 Glandular tissue 123 A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Lymph vessels Cancer cells spread through lymph and blood vessels to other parts of the body. Metastasis

61 Cancer cells have abnormal cell cycles –They divide excessively and can form abnormal masses called tumors Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division Growing out of control, cancer cells produce Malignant tumors

62 Breast cancer cell Figure 8.10x1

63 Mammograms Figure 8.10x2

64 Anti-Cancer drugs Colchicine: blocks microtubules from forming -binds & inhibits unpolymerized tubulin -breakdown of microtubules occur -polyploidy could occur Taxol: Found in the bark of yew trees -blocks ovarian cancer from forming

65 Genes that are thought to cause Cancer See Pgs: Oncogenes: a gene that increases cell division and triggers cancerous characteristics. Tumor Suppressor genes: a gene that inactivates or inhibits cell division. Prevents uncontrolled cell growth (cancer). It keeps mitosis in check and controls the cell cycle. Failure of normal cell programmed death (Apotosis) Pgs. 800 & 902

66 Stem Cells (pgs ) Undifferentiated cells Progenitor cells: partially specialized cell. an intermediate between a stem cell and a fully differentiated cell. Pluripotent cells: follows fewer pathways that it can develop into. Totipotent cells: cells that are very early in development when the zygote has developed into a small ball of cells.

67 Cell Differentiation

68 Evolution of Mitosis Chromosomes attach to the plasma membrane Chromosomes attach to the nuclear membrane Pass through the nucleus Spindle forms within the nucleus

69 Introductory Questions #3 1)Which phase is used to obtain pictures of chromosomes in order to generate a karyotype 2)3) Give five differences between Mitosis and Meiosis. 3)Name three factors in Meiosis & reproduction that contributes in increasing genetic variability within a population. 4)What is a polar body? How is oogenesis different from spematogenesis? 5)How is a sporophyte different from a gametophyte? What do they produce and what process is involved, mitosis or meiosis? 6)What is a tetrad? Which phase of Meiosis does crossing over occur?

70 Heredity, Life Cycles, and Meiosis Chapter 13

71 Heredity Heredity : the transmission of traits from one generation to the next Asexual reproduction : clones Sexual reproduction: variation Human life cycle : 23 pairs of homologous chromosomes 1 pair of sex chromosomes (X or Y) and 22 pairs of autosomes; Karyotype : Pix of chromosomes -Gametes are haploid (n) -All other cells (somatic) are diploid (2n) -Fertilization (syngamy) joining (fusion) of gametes to produce a zygote Meiosis: cell division to produce haploid gametes

72 The human life cycle Figure 8.13 MEIOSISFERTILIZATION Haploid gametes (n = 23) Egg cell Sperm cell Diploid zygote (2n = 46) Multicellular diploid adults (2n = 46) Mitosis and development

73 Alternative Life Cycles Fungi/some algae -Meiosis produces haploid cells (n) that divide by mitosis to produce -Haploid (n) adults (gametes produced by mitosis) Plants/some algae Do Alternation of generations: 2n = Sporophyte generation n = Gametophyte generation Meiosis occurs & produces spores: Spores are haploid (n) Spores divide by mitosis to generate more haploid cells (n) Gametes are produced by mitosis which then fertilize into a sporophyte (2n)

74 Human female karyotype Figure 8.19x2

75 Human male karyotype Figure 8.19x4

76 Meiosis Chromosome replicate 2 Cell divisions occur (Meiosis I & Meiosis II) 4 daughter cells are made all are (n): haploid Homologous Chroms separate in meiosis I Meiosis II = Mitosis (chromatids separate)

77 The differences between homologous chromosomes are based on the fact that they can carry different versions of a gene (alleles) at corresponding loci Homologous chromosomes carry different versions of genes

78 Homologous Chromosomes (Are they identical?) Sister Chromatids from father from mother Tetrad (Bivalent)

79 Figure 8.14, part 1 MEIOSIS I : Homologous chromosomes separate INTERPHASEPROPHASE I METAPHASE I ANAPHASE I Centrosomes (with centriole pairs) Nuclear envelope Chromatin Sites of crossing over Spindle Sister chromatids Tetrad Microtubules attached to kinetochore Metaphase plate Centromere (with kinetochore) Sister chromatids remain attached Homologous chromosomes separate

80 Crossing over is the exchange of corresponding segments between two homologous chromosomes Genetic recombination results from crossing over during prophase I of meiosis Crossing over further increases genetic variability

81 Figure 8.18A Tetrad Chaisma Centromere

82 Synaptonemal Complex- Pg 213 Protein that hold homologous chromosomes together Thought to be involved in crossing over events

83 How crossing over leads to genetic recombination Figure 8.18B Tetrad (homologous pair of chromosomes in synapsis) Breakage of homologous chromatids Joining of homologous chromatids Chiasma Separation of homologous chromosomes at anaphase I Separation of chromatids at anaphase II and completion of meiosis Parental type of chromosome Recombinant chromosome Parental type of chromosome Gametes of four genetic types Coat-color genes Eye-color genes

84 Figure 8.17A, B Coat-color genesEye-color genes BrownBlack CE ce WhitePink CE ce CE ce Tetrad in parent cell (homologous pair of duplicated chromosomes) Chromosomes of the four gametes

85 Origins of Genetic Variation (1) Independent assortment: How they line up during metaphase I Matters!!! Homologous pairs of chromosomes position and orient themselves Randomly. (random positioning) Different combinations are possible when gametes are produced.

86 Figure 8.16 POSSIBILITY 1POSSIBILITY 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Gametes Combination 1Combination 2Combination 3Combination 4

87 Origins of Genetic Variation (2) Crossing over (prophase I): -the reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I (recombinant chromosomes) (3) Random fertilization: 1 sperm (1 of 8 million possible chromosome combinations) x 1 ovum (1 of 8 million different possibilities) = 64 trillion diploid combinations!

88 Figure 8.14, part 2 MEIOSIS II : Sister chromatids separate TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II Cleavage furrow Sister chromatids separate TELOPHASE II AND CYTOKINESIS Haploid daughter cells forming

89 Meiosis vs. Mitosis Synapsis/tetrad/chiasmat a (prophase I) Homologous vs. individual chromosomes (metaphase I) Sister chromatids do not separate (anaphase I) Meiosis I separates homologous pairs of chromosomes, not sister chromatids of individual chromosomes.

90 Figure 8.15 MITOSISMEIOSIS PARENT CELL (before chromosome replication) Site of crossing over MEIOSIS I PROPHASE I Tetrad formed by synapsis of homologous chromosomes PROPHASE Duplicated chromosome (two sister chromatids) METAPHASE Chromosome replication 2n = 4 ANAPHASE TELOPHASE Chromosomes align at the metaphase plate Tetrads align at the metaphase plate METAPHASE I ANAPHASE I TELOPHASE I Sister chromatids separate during anaphase Homologous chromosomes separate during anaphase I ; sister chromatids remain together No further chromosomal replication; sister chromatids separate during anaphase II 2n2n2n2n Daughter cells of mitosis Daughter cells of meiosis II MEIOSIS II Daughter cells of meiosis I Haploid n = 2 nnnn

91 Introductory Questions #2 1) From our the overall data in our Mitosis lab, what stage was the shortest and which stage was the longest? If Telophase was supposed to be the shortest phase, what would have contributed to our different results? 2) Which phase is used to obtain pictures of chromosomes in order to generate a karyotype? 3) Give five differences between Mitosis and Meiosis. 4) Name three factors in Meiosis & reproduction that contributes in increasing genetic variability within a population. 5) What is a polar body? How is oogenesis different from spematogenesis? 6) How is a sporophyte different from a gametophyte? What do they produce and what process is involved, mitosis or meiosis? 7) What is a tetrad? Which phase of Meiosis does crossing over occur?

92 Translocation Figure 8.23Bx

93 At fertilization, a sperm fuses with an egg, forming a diploid zygote –Repeated mitotic divisions lead to the development of a mature adult –The adult makes haploid gametes by meiosis –All of these processes make up the sexual life cycle of organisms

94 The large number of possible arrangements of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametes Random fertilization also increases variation in offspring

95 Human female bands Figure 8.19x1

96 Human female karyotype Figure 8.19x2

97 Human male bands Figure 8.19x3

98 Human male karyotype Figure 8.19x4

99 Down syndrome karyotype Figure 8.20Ax

100 Klinefelters karyotype Figure 8.22Ax

101 XYY karyotype Figure 8.22x

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