cell division

• role of mitosis 


  to produce identical daughter cell for growth and asexual reproduction
• 4 stages of mitosis
• 4 stages of mitosis

  prophase, metaphase, anaphase, telophase
• mitosis stages


  -prophase: spindle fibers condens, chromosomes condence, spindle fibers attach to chromosoes. -metaphase: chromosomes align in middle. -anaphase:cetromers divide, sister chromatids move to seperate sides -telophase: nuclear membreame reforms, chromosomes decondense.

  
• interphase (mitosis)


  interphase occure before mieiosis
• interphase(mitosis)


  interphase-occur before mitosis, during this stage the cell grows and prepares to divide. chromosomes and some organelles' are replicated
• cytokinesis(mitosis)


  cytoplasm divide producing 2 daughter cells
• what is meiosis


  a cell division which gives rise to genetic variation. main role is to produce 4 haploid gametes which are genetically different
• stages of meiosis 2

  -prophase 11: nuclure envelope breaks down and chromosomes condense, spindle fibers form. -metaphase 11: chromosomes line up on equator. -anaphase 11: centomers divide, individuals chromatids are pulled to opposite sides -telophase 11: nuclure membrane form around eaxh group -cytokinesis 11: new cell membranes form creating 4 haploid cells
• interphase


  during interphases the cell increase in mass and size, synthsising proteins and replicating dna. it consisit of 3 phases: -g1 phase: cells make rna , enzymes and other proteins for growth -s phase: synthesis of dna -g2 phases: new dna is checked and any errors repaired
• Stages of meiosis 1

  1. Prophase 1

  2. Metaphase 1

  3. Anaphase 1

  4. Telophase 1

  5. Cytokinesis 1
• Prophase 1


  • DNA condense and become visible
  • 2 sister chromatids joined together be a centromere in homologous pairs (bivalent)
  • Centrioles migrate to opposite poles
  • Nuclear envelope breaks down
  • Crossing over of chromatids may occurs this is called chiasma
• Metaphase 1


  • Bivalents line up in middle along equator
  • Spindle fibres attach to centromeres
• Anaphase 1


  • Pairs are separated as microtubules pull chromosomes to opposite sides
• Telophase 1


  • Spindle fibres break down
  • Nuclear envelope reforms around 2 groups
• Cytokinesis 1


  1. Animal cells: cell surface membrane pinches in the middle dividing cytoplasm in half

  2. Plant cell: vesicles from golgi body line up on equator creating a membrane and secrete calcium which becomes primary and secondary wall of the cell