cells and control

• Mitosis


  A type of cell division that takes place in body cells
• Parent cell


  The cell that is dividing
• Daughter cells


  The two new cells that are formed
• If the parent cell is diploid, the daughter cells will be diploid too
• Stages of mitosis


  1. Interphase

  2. Prophase

  3. Metaphase

  4. Anaphase

  5. Telophase
• Mitosis


  • Produces two genetically identical cells
  • Diploid means double (two sets of chromosomes)
• in prophase Each chromosome consists of two chromatids
• in anaphase The chromatids separate and one chromatid from each pair is pulled to each pole of the cell
• At the end of mitosis, the cell divides into two - this is called cytokinesis
• During interphase, the DNA has already been copied before the chromosomes become visible
• During metaphase, the chromosomes line up along the middle of the cell
• During telophase, the spindle fibres disappear and a new nuclear membrane forms around each group of chromosomes
• The stages of mitosis can be remembered using the mnemonic IPMAT (Interphase, Prophase, Metaphase, Anaphase, Telophase)
• Body cells have two sets of chromosomes
• interphase


  like this

  
• prophase


  looks like this
• metaphase 


  ..

  
• anaphase 


  .

  
• telophase 


  .

  
• a cell is in interphase most of the time
• When mitosis happens


  • Growth
  • Repair (replacement of damaged cells)
  • Asexual reproduction
• Normally cells only divide by mitosis when new diploid cells are needed
• Asexual reproduction generates offspring that are genetically identical to a single parent.
• sexual

  reproduction, two parents contribute genetic information to produce unique offspring.
• Uncontrolled cell division


  Cancer cells are abnormal cells that divide uncontrollably by mitosis to form a tumour
• Cells usually stop dividing when growth has finished, except when repair is needed
• The controls that tell cells when to stop dividing go wrong


  This leads to cancer
• what is Cloning  


  the processes used to create an exact genetic replica of another cell, tissue or organism
• growth in animals


  an increase in an animal's size or mass over its lifetime
• growth in plants


  They grow through a combination of cell growth and cell division (mitosis). 
• why are percentile curves used to measure the growth of babies

  Because children grow at varying rates at different ages and along different tracks
• zones of growth in an onion root


  .

  
• what is differentiation 


  changing of a cell to a more specialized cell type
• what is a stem cell 


  cells that have the capacity to self-renew and to generate multiple mature cell types
• where are stem cells found

  in small numbers in most adult tissues, such as bone marrow or fat
• differences between adult and embryonic stem cells

  Embryonic stem cells are only found in embryos. They can differentiate into all the cell types that make a human. Adult stem cells are found in children and adults. They can only differentiate into a limited number of cell types.
• what are stem cells called in plants

   totipotent cells
• pros of stem cells

  regenerate and repair tissues that have been damaged or affected by disease. 
• cons of stem cells

  • Usually a very small number in each tissue making them difficult to find and purify.
• what is refreaction 


   a beam of light bending as the light's velocity changes