Mitosis

• Diploid cells - most body cells have two copies of each chromosome
• When cells divide, their chromosomes double beforehand

  • ensures that when the cell splits in two, each new cell still has two copies of each chromosome (is still diploid)
• Cell division is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction
• Mitosis - nuclear division giving rise to genetically identical cells
• Process of Mitosis

  A) replicated

  B) nucleus

  C) chromosomes

  D) nuclear membrane

  E) replicated

  F) chromosome

  G) duplicated

  H) nuclear membrane

  I) breaks

  J) centre

  K) centre

  L) chromosomes

  M) separated

  N) divide

  O) gentically

  P) identical

  Q) daughter

  
• Process:

  • Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x-shaped chromosomes)
  • Chromosomes line up along the centre of the cell where cell fibers pull them apart
  • The cell divides into two and each new cell has a copy of each of the chromosomes
• All cells in the body (excluding gametes) are produced by mitosis of the zygote
• Mitosis is important for replacing cells e.g. skin cells, red blood cells, production of new cells when a zygote divides to form an embryo
• Mitosis in growth - mitosis produces new cells
• Mitosis in repair - replaces damaged or dead cells
• Mitosis in asexual reproduction - mitosis produces offspring that are genetically identical to the parent
• Stem cells - unspecialised cells in small numbers in many tissues in the human body

  • divide by mitosis and produce new daughter cells that can become specialised within the tissue and be used for different functions
• Zygote - the ultimate stem cell

  • embryonic stem cells - a zygote divides several times by mitosis to become a ball of unspecialised cells
  • embryonic cells are all the same and start differentiating as the fetus develops with recognisable features
• Stem cells - unspecialised cells that divide via mitosis to produce daughter cells that can be specialised to do specific functions

  • already specialised cells cannot be specialised
• Cell cycle - cells in our body divide in a series of stages
• Cell division involves mitosis - produces 2 identical cells

  • needs their cells for growth and the replacement of damaged cells
• Steps of mitosis

  1. nucleus breaks down and chromosomes line up down the middle
  2. chromosomes are in pairs and then divide because they are duplicates of eachother
  3. they get moved to separate sides and then forms new nucleus
• Mitosis Process

  A) parent

  B) makes identical copies

  C) not mitosis but DNA replication

  D) Mitosis

  E) lines up along the centre

  F) move to either end

  G) cell divides

  H) 2 daughter cells formed

  
• Why is mitochondrion important for mitosis?

  Mitosis is a process that needs energy and mitochondria carries out aerobic respiration which releases energy