CELL CYCLE AND CELL DIVISION

• Cell - basic unit of life

  - all living organisms have cells
• Eukaryotic cell - Membrane-enclosed nucleus and organelles
• Prokaryotic cells -capsule, cell wall, nucleoid, flagellum
• Cell division - process cells undergo in order to survive

  - producing more cells from parent cells

  - reducing number in cells to produce gametes or sex cells
• Important Functions of cells:

  1. for development and growth
  2. replace worn-out or damaged cells
  3. produce sex cells or gametes
• Organelles involved in cell Division:

  1. Cell membrane- keeps all organelles inside cells and allows splitting of cells
  2. Nucleus - contains chromosomes
  3. Chromosomes - contains DNA
  4. Centrioles - duplicates and anchors spindle fibers
  5. Microtubules - acts as skeleton of cells
• The human body has 46 chromosomes, but gametes only have 23 chromosomes
• Cell cycle

  > cycle cells undergo
• Interphase - stages where cells grow

  - replicates DNA <----- S stage

  - grow and develop
• Mitosis - produce body cells

  - replace worn out or damaged cells

  - healing cuts and wounds

  -produce diploid cells ( chromosomes)
• Meiosis

  > produces sex cells

  > allows variety of differences in human characteristics

  > produces haploid cells (23 chromosomes)

  > "Reduction Division"
• Centrosome - sister chromatids

  Chromatids - strands of replicated chromosomes
• Cytokinesis - cells completely divides into two:

  1x mitosis

  2x meiosis

  - last process
• Stages of Mitosis

  Prophase - chromosomes condense and nucleus is still present

  Metaphase- chromos are aligned and nucleus is dissembled

  Anaphase - chromosomes are pulled away

  Telophase - nucleus are forming to create 2 new cells
• Stages of Meiosis

  Prophase 1 - chromosomes thickens and condense

  - "crossing over"

  Metaphase 1 - chromos in pairs, aligned in the middle

  Anaphase 1 - pulled away

  telophase 1 - you have newly formed nuclei
• Stages of Meiosis 2

  Prophase 2 - you have 2 cells

  Metaphase 2 - chromos are aligned but is not in pairs

  Anaphase 2 - pulled away

  Telophase 2 - 2 cells diided into 4
• Crossing over - when homologous chromosomes exchange genetic information during meiosis