Presentation on theme: "Mitosis and Meiosis Chapter 12 & 13 Mitosis & Meiosis."— Presentation transcript:
1Mitosis and MeiosisChapter 12 & 13Mitosis & Meiosis
2Next Unit: Genetics & DNA Chapter 12 & 13: Mitosis & MeiosisChapter 14: Principles of HeredityChapter 15: Human Genetics & DisordersChapter 16: DNA: History, Structure & Function**Three Labs will be done for this UnitGoal: to complete before Thanksgiving and to take Test #3 on 11/20 (Tuesday)
3Video #1: Generations-Mitosis & Meiosis In the mid 1800’s 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?Chromosomes literally mean: “_______”What is a centromere and what is its function?What is a karyotype and what does it reveal? What are “homologous chromosomes”?How many chromosomes do humans, fruit flies (Drosophila), horsetails, Toads, and pea plants have?Name the business used in the 2nd segment to show the importance of mitosis.Briefly explain what “grafting” is?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. 221Name the FOUR phases of Mitosis and two key events that occur. (See pg )Name two differences between Mitosis & Meiosis after watching the final segment.****Write the Title for each segment and THREE key statements for each segment.
4Introductory 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?
5Mitosis Occurs only in certain types of cells Form of asexual reproductionProduces two genetically identical cells from one cell.The splitting or dividing of the nucleusViewed in different stages by examining chromosome formation and behavior.
6Significance of Understanding Mitosis Preserves the continuity of lifeAllows organisms to grow, repair, and reproduceImportant in unlocking the mysteries of embryonic development & stem cellsImportant in understanding how cancer develops and could someday provide clues in stopping cancer.
7Cell replacement (seen here in skin) Dead cellsEpidermis, the outer layer of the skinDividing cellsDermisFigure 8.11B
8Packaging of Genetic Material http://www. biostudio Structure / Activity DiameterDNA: 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)
9Chromosomes 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”
10Cells from an onion Root tip When the cell cycle operates normally, mitotic cell division functions in:Growth (seen here in an onion root)Figure 8.11A
12Asexual reproduction (seen here in a hydra) Figure 8.11C
13THE EUKARYOTIC CELL CYCLE AND MITOSIS A eukaryotic cell has many more genes than a prokaryotic cellThe genes are grouped into multiple chromosomes, found in the nucleusThe chromosomes of this plant cell are stained dark purpleFigure 8.4A
16Before a cell starts dividing, the chromosomes are duplicated Sister chromatidsBefore a cell starts dividing, the chromosomes are duplicatedCentromereThis process produces sister chromatidsFigure 8.4B
17Chromosome distribution to daughter cells When the cell divides, the sister chromatids separateChromosome duplicationSister chromatidsCentromereTwo daughter cells are producedEach has a complete and identical set of chromosomesChromosome distribution to daughter cellsFigure 8.4C
19TELOPHASE AND CYTOKINESIS METAPHASEANAPHASETELOPHASE AND CYTOKINESISCleavage furrowNucleolus formingMetaphase plateNuclear envelope formingSpindleDaughter chromosomesFigure 8.6 (continued)
20The Cell Cycle: Generation Time Interphase: most of a cell’s life (90%)-G1: 1st gap of growth-S phase: DNA is duplicated(synthesized)-G2 phase: 2nd gap of growthMitosis: splitting of the nucleus (PMAT)Cytokinesis: separation of the cytoplasm
21The cell cycle multiplies cells The cell cycle consists of two major phases:Interphase, where chromosomes duplicate and cell parts are madeThe mitotic phase, when cell division occursFigure 8.5
23Interphase Cells spend most of its time in this phase Cells are growingDNA has to be replicated (all 2 meters of it)Proteins are being produced90% of all cells are in this phaseThree phases: G1, S, and G2
25Prophase 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 nucleusNuclear membrane (envelope) disappearsMicrotubules elongate forming the spindle apparatus
31Anaphase 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.
34Cytokinesis differs for plant and animal cells In animals, cytokinesis occurs by cleavageThis process pinches the cell apartCleavage furrowCleavage furrowContracting ring of microfilamentsFigure 8.7ADaughter cells
35In plants, a membranous cell plate splits the cell in two Cell plate formingWall of parent cellDaughter nucleusIn plants, a membranous cell plate splits the cell in twoCell wallNew cell wallVesicles containing cell wall materialCell plateDaughter cellsFigure 8.7B
36Cells from an onion Root tip When the cell cycle operates normally, mitotic cell division functions in:Growth (seen here in an onion root)Figure 8.11A
44Total Class Data for all Three Classes: Fall 2005
45Total Class Data for all Three Classes: Fall 2006
46Regulation of Cell Division Driven by specific molecular signalsResearch has shown:Two cells in different phases causes the other to be pushed into the next phases.Ex.S phase & G1 grown together will cause the G1 cell to enter into the S phase immediatelyM phase cell & G1 cell will cause the G1 cell to enter into the M phase immediately.There is an obvious control system in place.
47Regulating Mitosis-Control System (pg. 229-231) Most cells can divide up to 50 timesControl of the Cell cycle involves three checkpoints-G1 (most important checkpoint) = restriction point(G0: non-dividing state)-G2-M phaseGrowth factors (proteins): Cyclins & KinasesKinases: phosphorylate proteins, gives the go aheadCdk: are kinases that must be attached to a cyclin to be activatedMPF: Maturation promoting factor (Fig: pg. 230)Complex of kinase and cyclinTriggers the passage from G2 phase into M phasepeaks during Metaphase
48Growth factors signal the cell cycle control system Proteins within the cell control the cell cycleSignals affecting critical checkpoints determine whether the cell will go through a complete cycle and divideG1 checkpointControl systemM checkpointG2 checkpointFigure 8.9A
49Cyclin & Kinase effects on the cell cycle. Animated link:
50Introductory Questions #2 Which checkpoint in the regulation of mitosis is considered the “restriction point”? Why point and not the others?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.Why are telomeres considered to be a “mitotic clock”?How are tumor supressor genes different from an oncogene? What is the difference between a malignant tumor and a benign tumor?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?
52Growth 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 conditionsCytokinins: key hormone in plants that promotes cell division
53Cell cycle control system The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell divisionGrowth factorPlasma membraneRelay proteinsReceptorproteinG1 checkpointSignal transduction pathwayCell cycle control systemFigure 8.8B
54Mitotic 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 times1,200 nucleotides are removed after each mitotic event
57Anchorage, cell density, and chemical growth factors affect cell division Most animal cells divide only when stimulated, and others not at allIn laboratory cultures, most normal cells divide only when attached to a surfaceThey are anchorage dependent
58Cells continue dividing until they touch one another This is called density-dependent inhibitionCells anchor to dish surface and divide.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).Figure 8.8A
59Growth factors are proteins secreted by cells that stimulate other cells to divide See pg. 232After forming a single layer, cells have stopped dividing.Providing an additional supply of growth factors stimulates further cell division.Figure 8.8B
60Malignant tumors can invade other tissues and may kill the organism Lymph vesselsTumorGlandular tissueMetastasis1A tumor grows from a single cancer cell.2Cancer cells invade neighboring tissue.3Cancer cells spread through lymph and blood vessels to other parts of the body.Figure 8.10
61Growing out of control, cancer cells produce Malignant tumors Cancer cells have abnormal cell cyclesThey divide excessively and can form abnormal masses called tumorsRadiation and chemotherapy are effective as cancer treatments because they interfere with cell division
64Anti-Cancer drugs Colchicine: blocks microtubules from forming -binds & inhibits unpolymerized tubulin-breakdown of microtubules occur-polyploidy could occurTaxol: Found in the bark of yew trees-blocks ovarian cancer from forming
65Genes that are thought to cause Cancer See Pgs: 371-372 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
66Stem Cells (pgs. 415-418) 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.
68Evolution of Mitosis Pass through the nucleus Chromosomes attach to the plasma membraneChromosomes attach to the nuclear membranePass through the nucleusSpindle forms within the nucleus
69Introductory Questions #3 Which phase is used to obtain pictures of chromosomes in order to generate a karyotype3) Give five differences between Mitosis and Meiosis.Name three factors in Meiosis & reproduction that contributes in increasing genetic variability within a population.What is a polar body? How is oogenesis different from spematogenesis?How is a sporophyte different from a gametophyte? What do they produce and what process is involved, mitosis or meiosis?What is a tetrad? Which phase of Meiosis does crossing over occur?
71HeredityHeredity: the transmission of traits from one generation to the nextAsexual reproduction: clonesSexual reproduction: variationHuman life cycle:23 pairs of homologous chromosomes1 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 zygoteMeiosis: cell division to produce haploid gametes
72Multicellular diploid adults (2n = 46) Mitosis and development The human life cycleHaploid gametes (n = 23)Egg cellSperm cellMEIOSISFERTILIZATIONDiploid zygote (2n = 46)Multicellular diploid adults (2n = 46)Mitosis and developmentFigure 8.13
73Alternative 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 algaeDo Alternation of generations:2n = Sporophyte generationn = Gametophyte generationMeiosis 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)
76Meiosis Chromosome replicate 2 Cell divisions occur (Meiosis I & Meiosis II)4 daughter cells are made all are (n): haploidHomologous Chrom’s separate in meiosis IMeiosis II = Mitosis(chromatids separate)
77Homologous chromosomes carry different versions of genes The differences between homologous chromosomes are based on the fact that they can carry different versions of a gene (alleles) at corresponding loci
78Homologous Chromosomes (Are they identical?) Tetrad (Bivalent)♂ from fatherfrom motherSister Chromatids
79MEIOSIS I: Homologous chromosomes separate INTERPHASEPROPHASE IMETAPHASE IANAPHASE ICentrosomes (with centriole pairs)Microtubules attached to kinetochoreSites of crossing overMetaphase plateSister chromatids remain attachedSpindleNuclear envelopeChromatinSister chromatidsTetradCentromere (with kinetochore)Homologous chromosomes separateFigure 8.14, part 1
80Crossing over further increases genetic variability Crossing over is the exchange of corresponding segments between two homologous chromosomesGenetic recombination results from crossing over during prophase I of meiosis
82Synaptonemal Complex- Pg 213 Protein that hold homologous chromosomes togetherThought to be involved in crossing over events
83How crossing over leads to genetic recombination Coat-color genesEye-color genesHow crossing over leads to genetic recombinationTetrad (homologous pair of chromosomes in synapsis)1Breakage of homologous chromatids2Joining of homologous chromatidsChiasmaSeparation of homologous chromosomes at anaphase I3Separation of chromatids at anaphase II and completion of meiosis4Parental type of chromosomeRecombinant chromosomeRecombinant chromosomeParental type of chromosomeFigure 8.18BGametes of four genetic types
84C E C E C E c e c e c e Coat-color genes Eye-color genes Brown Black WhitePinkTetrad in parent cell (homologous pair of duplicated chromosomes)Chromosomes of the four gametesFigure 8.17A, B
85Origins of Genetic Variation (1) Independent assortment:How they line up during metaphase IMatters!!!Homologous pairs of chromosomesposition and orient themselvesRandomly. (random positioning)Different combinations are possible when gametes are produced.
86Two equally probable arrangements of chromosomes at metaphase I POSSIBILITY 1POSSIBILITY 2Two equally probable arrangements of chromosomes at metaphase IMetaphase IIGametesCombination 1Combination 2Combination 3Combination 4Figure 8.16
87Origins of Genetic Variation (2) Crossing over (prophase I):-the reciprocal exchange ofgenetic material betweennonsister chromatids duringsynapsis 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!
88MEIOSIS II: Sister chromatids separate TELOPHASE I AND CYTOKINESISTELOPHASE II AND CYTOKINESISPROPHASE IIMETAPHASE IIANAPHASE IICleavage furrowSister chromatids separateHaploid daughter cells formingFigure 8.14, part 2
89Meiosis vs. Mitosis http://www.pbs.org/wgbh/nova/baby/divi_flash.html Synapsis/tetrad/chiasmata (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.
90PARENT CELL (before chromosome replication) Site of crossing over MITOSISMEIOSISPARENT CELL (before chromosome replication)Site of crossing overMEIOSIS IPROPHASEPROPHASE ITetrad formed by synapsis ofhomologous chromosomesDuplicated chromosome (two sister chromatids)Chromosome replicationChromosome replication2n = 4Chromosomes align at the metaphase plateTetrads align at the metaphase plateMETAPHASEMETAPHASE IANAPHASE ITELOPHASE IANAPHASE TELOPHASESister chromatids separate during anaphaseHomologous chromosomes separate during anaphase I; sister chromatids remain togetherHaploid n = 2Daughter cells of meiosis I2n2nNo further chromosomal replication; sister chromatids separate during anaphase IIMEIOSIS IIDaughter cells of mitosisnnnnDaughter cells of meiosis IIFigure 8.15
91Introductory 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?
93At fertilization, a sperm fuses with an egg, forming a diploid zygote Repeated mitotic divisions lead to the development of a mature adultThe adult makes haploid gametes by meiosisAll of these processes make up the sexual life cycle of organisms
94The large number of possible arrangements of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametesRandom fertilization also increases variation in offspring