Mitosis and Meiosis

• Mitosis

  • if a cell wants to make a duplicate of itself, it must copy its DNA
  • the copies then must be separated and sorted into two sides of the cells
  • the cell then splits in two. Part of each parent is carried to the two new cells
  • results in cells such as internal organs, skin, bones, blood, etc.
• Meiosis

  • as in mitosis, if a cell wants to make a duplicate of itself , it first must copy the its DNA ( part of chromosomes )
  • result in reproductive cells ( sperm , eggs , etc. )
  • part of each parent is carried to the four new cells
  • meiosis has evolved to solve a problem
  • the problem is this: some organisms mate with other organisms - that is, they combine their genes together ( creating genetic diversity )
• Remember

  • MITosis takes the cell and Makes It Two ( diploid )
  • Meiosis has to do with sexual reproduction

  from the cells point of view :

  • mitosis result in identical twins
  • meiosis results in egg and sperm ( haploid )
• Vocabulary

  • diploid
  • haploid
  • Interphase - Prophase - Metaphase - Anaphase - Telophase - Cytokinesis 
• Interphase occurs just before mitosis begins :

  • DNA is replicated along with organelles and other cellular components and the cell prepares for division.
• 1st step in Mitosis: Prophase (preparation phase)

  • The DNA recoils , and the chromosomes condenses
  • the nuclear membrane disappears and the mitotic spindles begin to form
• 2nd Step in mitosis: Metaphase ( organizational phase )

  • the chromosome line up the middle of the cell with the help of spindle fibers attached to the centromere of each replicated chromosome.
• 3nd Step in mitosis: Anaphase ( separation phase )

  • the chromosomes split in the middle and the sister chromatids are pulled by the spindle fibers to opposite poles of the cell.
• 4th step in mitosis: telophase

  • the chromosome, along with the cytoplasm and it organelles and membranes are divided into 2 portions
  • this diagram shows the end of telophase
• After mitosis : cytokinesis

  • the actual splitting of the daughter cells into two separate cells is called cytokinesis and occurs differently in both plant and animal cells
• Meiosis Interphase

  • Meiosis is preceded by interphase. The chromosomes have not yet condensed. • The chromosomes have replicated, and the chromatin begins to

  condense.
• Meiosis Prophase

  • The chromosomes are completely condensed. In meiosis (unlike mitosis), the homologous chromosomes pair with one another