CELL DIVI , MITOSIS

• - allows multicellular organisms to grow- reproduce and create identical copies of themselves- repair damaged or dead cells in multicellular organisms


  why do cells divide
• reproduction


  a process amonglife forms to make a new organismform one or two organism• Asexual and Sexual reproduction
• binary fission


  A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size
• cell replacement


  Wound healing involves growth of newcells out of cell division.
• cell division


  occurs in the red bonemarrow of your bones (in ribs,breastbone, vertebrae, and hips) tocontinuously make new red blood cells to replace the dying ones.
• chromosomes


  where the DNA a double-stranded molecule istightly coiled.-A long, continuousthread of DNA iswounded togetherby histones.
• chromatin


  a macromolecule thatcontains loose DNA, protein, andRNA.
• chromatid


  refers toeach strand of theduplicated chromosomes
• sister chromatids


  are held together bycentromere.
• telomeres


  contain repeated nucleotides that donot translate into traits. They prevent the loss of genes.
• cell cycle


  1. Interphase2. Mitosis3. Cytokinesis
• interphase


  Gap 1, Synthesis, Gap 2- Cells carry outtheir normal functions.• The growth period in the cellcyle.
• Gap 1

  Cells carry out normalmetabolic functions- increase in size as cell organellesincrease in number- embryonic cell divide rapidly- cells spend most of their life cycle inthis phase though length differs* Cells haverequired size limitprevent the cell from starting the Sstage, until a growth-promoting signal hasbeen received
• synthesis


  dna replicationmakes copies of chromosomesproduce a copy of microtubules for cell organization
• gap 2

  caqrry out normal functionsundergo further growthhas a critical checkpoint to check cell size and dna duplication checkpoint verifies that the cells DNAhas been copied before mitosis can occur
• mitosis


  cell is active and full of activity.• Involves division of nucleus• Hereditary materials of the parent cell is given to thedaughter cells.• 4 parts - Prophase, Metaphase, Anaphase and Telophase
• cytokinesis

  - division of the cytoplasm.• -begins early during telophase and continues afterthe nuclei have formed in the daughter cells.- division of the cytoplasm- CLEAVAGE FURROW IN ANIMAL CELLS- FORM CELL PLATE IN PLANT
• prokaryotic cells


  divide morerapidly than eukaryotic cells becausethey lack membrane-boundorganelles and cytoskeleton.
• prophase


  first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus. spindle fibers assemble
• metaphase


  The spindle fibers attachto the kinetochore of thesister chromatids tofacilitate the movementof chromosomes toward• the middle of the cell.Chromosomes lineup along theequatorial plane.
• anaphase


  • Cohesion breaksdown and the sisterchromatids separatefrom each other.• Spindle fibers shortenand pull the sisterchromatids to theopposite ends of thecell.
• telephase


  • Two complete sets ofidentical chromosomesare now positioned ateach pole of the cell.Telophase: Reformationof Nuclei• Microtubule and spindlefiber disintegrates.• Nuclear membranereforms.• Chromosomes becomeless condensed.
• FACTORS THAT REGULATE CELL DIVISION

  - EXTERNAL GROWTH FACTORS- KINASE- CYCLINS- TRIGGERED CELL CYCLE ACTIVITIES
• Contact Inhibitions, Anchorage dependence, growth factors

  external factors
• contact inhibition


  cells stop dividing when they touch one another
• anchorage dependence


  cells only grow if surface is available and stop dividing when detached from the culture dish
• growth factors


  stimulate cell division by activating specific genes to trigger cell growth
• kinases cyclins, checkpoints, maturation

  internal factors
• kinases and cyclins


  help cells advance to different stages of the cell cycle
• kinase


  an enzyme thattransfers aphosphate groupfrom onemolecule to thetarget molecule.• help control cellcycle
• checkpoints


  prevent cell from proceeding to next stage util all requirements are met (e.g. g1 g2)
• maturation


  triggers the cells to pass through g2 checkpoint to undergo mitosis
• apoptosis


  • The orderly programmed cell deathor suicide.• The body's way to eliminate cellsthat are no longer functioning.• It occurs when the internal orexternal signals activate the genesresponsible for producing self-destructive enzymes.
• cancer


  • Refers to a group of diseasescharacterized by uncontrolledand abnormal cell division due toa disruption in the cell cycle.• Cancerous cells dividecontinuously forming tumors.• Tumors are either benign (harmless) or malignant (toxic).
• benign


  clustered together, harmless or not, curable
• malignant


  break away or metastasize; can be transported through the bloodstream and transfer to other body parts.
• oncogenes


  accelerate the cell cycle; carried by viruses
• carcinogens


  chemicals that cause develipment of cancers