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DNA and Cell Division. Mitosis in Animals. Background Information. Once an egg becomes fertilized, cellular divisions begins, eventually producing a whole organism. All cells derived from the zygote contain the same genetic material. An Integrated Organism. Organization of DNA. - PowerPoint PPT Presentation


  • DNA and Cell Division

  • Mitosis in Animals

  • Background Information Once an egg becomes fertilized, cellular divisions begins, eventuallyproducing a whole organismAn Integrated Organism

    All cells derived from the zygote contain the same genetic material

  • Organization of DNAAll cells have DNA (chromosomes).Almost all cells divide for reproduction, growth or repair.Each new cell needs the exact same DNA as the original cell.The original cell is called the mother cell and the two new cells are called daughter cells.The DNA in the nucleus must replicate before the cell divides.

  • Chromosome Number in Different Species

    Common NameGenus and SpeciesDiploid Chromosome NumberBuffaloBison bison60CatFelis catus38CattleBos taurus, B. indicus60DogCanis familiaris78DonkeyE. asinus62GoatCapra hircus60HorseEquus caballus64HumanHomo sapiens46PigSus scrofa38SheepOvis aries54

  • Number of genes in sequenced genomesE. coli4300Yeast6000Roundworm18,600Fruit fly13-14,000Mosquito13-14,000Mouse30-35,000Human30-35,000

  • A non-dividing cell:90% of a cells life is spent growing, not dividingThis phase is called interphaseThe DNA in this phase is not condensed; thus is chromatinAt some point during this phase the DNA is doubled or replicatedTwo copies are made, one for each of the new cells

  • Once replication occurs, the chromatin folds up to form chromosomesThis only occurs when the cell is about to divideThe duplicated chromosomes attach to each other at the centromereEach individual copy of one chromosome is known as a chromatidWhen chromatids are joined at the centromere, they are known as a single chromosome.

  • A piece of DNA or chromosome in an undividing cell Same piece now has replicated and super coiled ready for cell division.sister chromatidscentromere

  • Also during interphaseAdditional organelles are producedCell membrane enlarged to allow cell growthWhen the cell becomes too big to function it must divideWhat would the SA/V ratio of this cell belarge or small?

  • InterphaseThe cell growsNew organelles are formedDuplicate chromosomes are producedThe chromosomes are uncoiled and invisibleThis uncoiled chromosomes are known as a chromatin

  • Cell division/reproductionInterphase is not considered to be part of cell reproduction.It is simply the growth of the cell and the duplication of the chromosomes.Cell reproduction consists of two separate stages known as mitosis and cytokinesis.Cell division = mitosis + cytokinesisA parent cell will produce 2 daughter cells.

  • In cell division each chromosome is replicated and then the cell (and nucleus) divides

  • Cell ReproductionOriginal cell divides into two genetically identical daughter cellsComplete set of genetic information passed onto each daughter cellDNA must be accurately duplicated before cell divisionMitosis: paired chromatids separate and move to opposite ends of the cellCytokinesis: cytoplasm + organelles divide into roughly equal halves

  • http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swfMitosis Animation

  • MITOSIS/ CELL DIVISIONStages include:ProphaseMetaphaseAnaphaseTelophase

  • MitosisCentromeres align at cells equatorNucleolus disappears; Nuclear envelope breaks downMicrotubules attach to CentromeresChromosomes condense and shortenCentrioles begin to move apart;Spindle formsDuplicated chromosomes remain elongatedCentrioles have also been duplicatedLate InterphaseEarly ProphaseLate ProphaseMetaphase

  • Mitosis:Spindle fibers pull chromatids to opposite polesChromatids become independent chromosomesChromosomes begin unwindingNuclear envelope re-forms, spindle fibres disappearCytoplasm divided along equatorEach daughter gets 1 nucleus & half of cytoplasmAnaphaseTelophaseCytokinesisNext Interphase

  • ProphaseChromatin condenses (into chromosomes)Chromosomes appear as Xs.Nuclear envelope dissolves (DNA free in cell)Animals cells only: Centrioles move to opposite ends of cell + form spindle fibersCentromere attaches to spindle fibre

  • MetaphaseEach chromosome lines up in the middle of the cell.Highly organized so that both cells get exactly the same DNA.Spindle fibers attached to centromeres of chromosomes

  • AnaphaseEach pair of chromatids splits at the centromereEach chromatid is now an individual chromosome Paired chromosomes are pulled to opposite ends by spindle fibres

  • TelophaseChromosomes end up at separate poles, spindle fibers begin to dissolve.New nuclear envelope begins to form around chromosomeschromosomes begin to uncoilCell starts to pinch off through cytokinesis

  • CytokinesisDivision of all the rest of cell parts but not equally (organelles)Animals: cell membrane pinches to form two cellsPlants: new cell plate created between the two cells (becomes cell wall)

  • The Cell Cycle: An Overview1)Interphase




    Cell Division (Cell Reproduction) = mitosis + cytokinesis

  • Use an AcronymFor Mitosis: Prophase = PMetaphase = MAnaphase = ATelophase = TMake a sentence: Please Meet At TenPhil, Mary, And Tom

  • Figure 11-2

  • Linkshttp://en.wikipedia.org/wiki/Trisomy#Trisomyhttp://www.medgen.ubc.ca/wrobinson/mosaic/mos_how.htm

  • Mitosis DrawingFold a large sheet of paper in 3You should have 3 columns on the front and 3 on the backYou will draw a cell in each stage of mitosis and include a written description of what is occurring at each stageStages: Interphase, Prophase, Metaphase, Anaphase, Telophase, CytokinesisNotice that there are 6 stages and 6 coulmns on your sheet...1 stage per column!

  • Some facts500,000 deaths per year (more males)Older age group stricken more oftenMore than 100 types of cancer, many due to mutations triggered by environmental factorsHighest cancer incidence: male - prostatefemale - breastHighest cancer deaths: lung

  • Normal cells in cultureOrganized structureLimited cell growthNo overlapping

  • Cancer cells in cultureDisorganizedOverlapping structureUncontrolled cell growth

  • Some images to make this real: look first at normal skin

  • Cancerous Skin

  • What causes a normal cell to become a cancer cell?

  • Figure 9.00

    This scanning electron micrograph shows human sperm attempting to enter an egg. This chapter introduces the type of cell division called meiosis, which occurs prior to gamete formation.Figure: 11.8

    Title:A human male karyotype

    Caption:Staining and photographing the entire set of chromosomes within a single dividing cell produces a karyotype. Pictures of the individual chromosomes are cut out and arranged in descending order of size. The chromosomes occur in pairs (homologues) that are similar in both size and staining patterns and have similar genetic material. If these chromosomes were from a female, the cell would usually contain two X chromosomes. Notice that the Y chromosome is much smaller than the X chromosome. Figure: 11.7

    Title:Human chromosomes during mitosis

    Caption:The DNA and associated proteins in these human chromosomes have coiled up into the thick, short sister chromatids attached at the centromere. Each strand of texture is a loop of chromosome. During cell division, the condensed chromosomes are about 5 to 20 micrometers long. At other times, the chromosomes uncoil until they are about 10,000 to 40,000 micrometers long. Figure: 11.9

    Title:The eukaryotic cell cycle

    Caption:The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases. Figure: 11.11a-d

    Title:The cell cycle in an animal cell

    Caption:(a) Late interphase: The chromosomes have been duplicated but remain elongated and relaxed within the nucleus. The centrioles have also been duplicated. (b) Early prophase: The chromosomes condense, shortening and thickening. The centrioles begin to move apart, and the spindle microtubules begin to form between them. (c) Late prophase: The nucleolus disappears; the nuclear envelope breaks down, and the spindle microtubules attach to the kinetochore of each sister chromatid (red spot). (d) Metaphase: Interactions between the kinetochores and the microtubules have lined up the chromosomes at the cells equator. Figure: 11.11e-I

    Title:The cell cycle in an animal cell

    Caption:(e) Anaphase: Chromatids separate at the centromere, becoming independent chromosomes that move toward the opposite poles of the cell. The free spindle microtubules slide past one another, pushing the poles farther apart. (f) Telophase: One complete set of chromosomes reaches each pole. The chromosomes relax into their extended state, the spindle microtubules begin to disappear, and the nuclear envelopes begin to re-form. (g) Cytokinesis: At the end of telophase, the cytoplasm is divided along the equator of the parent cell, with each daughter cell receiving one nucleus and about half the original cytoplasm. (h) Interphase of daughter cells: The daughter cells enter interphase. The spindle microtubules disappear, the nuclear envelope re-forms, the chromosomes finish extending, and the nucleolus reappears. During the animation, disregard all the words, particularly the phase namesKeep track of the following:Cell membraneNuclear membraneChromosomesWhat is the result of mitosis & cytokinesis ?We will summarize afterFigure: 11.2

    Title:Mitotic cell division in eukaryotic cells produces cells needed for growth, development, and maintenance and repair

    Caption:Mitotic cell divisions produce the cells that make up the body of an embryo . Mitotic cell divisions


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