Cell Cycle

• MITOSIS


  Division of chromosomes

  Purpose:

  • Asexual reproduction
  • growth and replacement of dead cells

  Process:

  • clones the original parent cell
  • daughter cells are genetically identical to the parent cell
  • one cell division

  Location:

  • all somatic tissues

  Outcomes:

  • 2 identical daughter cells
• Meiosis


  Purpose:

  • creation of eggs and sperm for sexual reproduction

  Process:

  • number of chromosomes set halved
  • daughter cells contain half the DNA of the parent cell and the DNA is "mixed up" through
  • 2 cell division

  Location:

  • sexual organs only

  Outcome:

  • 4 genetically different eggs or sperm
• Interphase

  • period of cell growth and development

  1. G1 Phase - cell also grows, carries out normal cell activities, replicates all other organelles.
  2. S phase - DNA replicated; takes up responsibilities of DNA replication
  3. G2 Phase - enzyme and protein synthesis; centrosome replication completion; allow cell to grow more; prepares cells from mitosis
• Mitosis

  • precise process of nuclear division taht ensures each of the daughter cells receives 46 chromosomes each
  • cell cloning
  • accompanied by cytokinesis
  • occurs in all the somatic cells
• Prophase

  • condensation of chromosomes
  • centrioles move apart to begin mitotic
  • start nuclear envelope disintegrates
• Metaphase

  • position changing phase
  • microtubules align the centrosomes of the chromatid pairs at the equatorial plate
  • mitotic spindle forms: End/ poles of spindle - it is where microtubules converge
  • Types:

  1. those that anchor the centrosome to the cell membrane
  2. those that arc between the centrosome
  3. those that become attached to the chromosomes
• Anaphase

  • apart phase; shortest in the cycle; chromatids separate
  • spindle fibers pull chromosomes to opposite poles
  • cleavage furrow appears
• Telophase

  • 2 new nuclei are formed
  • chromosomes uncoil
  • nuclear envelopes form
  • completion of cytokinesis
  • spindle fibers disappear
• Cytokinesis

  • the division of the rest of the cell after the nucleus divides
  • In animal cells that cytoplasm pinches in
  • In plant cells a cell plate forms
• Reproductive cell division

  • consist of 2 nuclear division
  • occurs among sex cells
  • the ending cells will only have 23 chromosomes
• Meiosis

  • begin with diploid cells and ends with two diploid cells
• Prophase I

  • chromosomes will condense and thicken, and where they line up with their homologous pair: crossing over - trade part chiasmata keeps homologous pair together
  • starting cell is diploid (2n=4) homologous chromosomes pair up and exchange fragments (crossing over)
• Metaphase I

  • homologous chromosomes pair will line up at the metaphase plate for separation
  • homologous pairs line up at the metaphase plate
• Anaphase I

  • the homologous pair is pulled apart by spindle fibers and moves apart to opposite ends of the cells
  • homologous separate to opposite ends of the cell sister chromatids stay together
• Telophase I

  • the arrival of the chromosomes at the opposite poles of the cell
  • newly forming cells are haploid (n=2) each chromosomes has two (non-identical) sister chromatids
• Meiosis II

  • each of two haploid cells divides
• Prophase II

  • chromosomes condense
  • starting cells are the haploid cells made in Meiosis I; chromosomes condense
• Metaphase II

  • the chromosomes line up individually along the metaphase plate
  • chromosomes line up at metaphase plate
• Anaphase II

  • the sister chromatids separate and are pulled towards th opposite poles at the cells
  • sister chromatids separate to opposite ends of the cell
• Telophase II

  • nuclear membrane form around each set of chromosomes and the chromosomes decondense
  • newly forming gametes are haploid, each chromosome has just one chromatids
• Cytokinesis

  • splits the chromosomes sets into new cells, forming the final products of meiosis; four haploid cells
• Mitosis is used when an organism needs to grow or repair itself.
• Interphase includes G0 phase, where cells stop dividing and become specialized, G1 phase, S phase, and G2 phase.