cell division + differentation

• meiosis

  result in sex cells (gametes)

  have half of original chromosome cells

  sexual reproduction

  doubles --> splits --> halves
• mitosis

  produces identical cells

  same chromosomes

  same genetic info

  asexual reproduction

  doubles --> splits
• differentiation

  stem cells become specialised cells by mitosis

  in animals cells it happens early

  in plant cells it happens throughout its life - move a cell into a different area and it will re-differentiate
• cloning

  produce identical offspring

  easier to clone a plant

  cloning of animals have to be done at embryo stage

  cloning of plants can be done at any time
• fertilisation

  fusion of sex cells

  body cells twos (pair) sets of chromosomes while sex cells only have one (single)
• bone marrow

  good source of stem cells
• get stem cells from umbilical cord and not foetus
• cell cycle

  active cell division

  interfase -> no cell division taking place, replicating dna, carrying out normal cell activites

  cell gets bigger
• cell cycle slows down after puberty
• tumour formation

  divides rapidly

  mitosis is fast and interface is small
• benign

  grows in one place

  it does not affect other tissues

  grows rapidly and puts pressure on other cells or tissues around it
• malignant (cancer)

  can travel around the body and damage other cells / tissues

  break apart other cells

  tumour might split and go into bloodstream meaning it spreads
• causes of cancer

  • result of mutations
  • genetic info is changing
  • chemicals eg. tar in tobacco
  • carcinogens
  • ionising radiation - eg. UV light, x-rays
  • virus infections