cell differentiation, chromosomes & mitosis

• differentiation


  when a cell becomes specialised for its job
• undifferentiated cells are called


  stem cells
• cells that differentiate in mature animals are mainly used for

  repairing and replacing cells such as skin or blood cells
• why is differentiation needed

  for growth, repair and replacement
• name types of specialised cells

  sperm, nerve, muscle, root hair, phloem and xylem
• how are sperm cells specialised for reproduction


  long tails to help swim. lots of mitochondria for energy. enzymes to digest though egg
• how are nerve cells specialised for rapid signalling

  long to cover more distance. branched connections to connect to other nerve cells to create a network throughout the body
• how are muscle cells specialised for contraction

  cells are long. lots of mitochondria to generate energy for contraction
• how are root hair cells specialised for absorbing water and mineral

  long hairs that stick out of the soil to give plants a large surface area for absorbing water and mineral ions from the soil. lots of mitochondira for active transport
• how are phloem and xylem cells specialised for transporting substances


  cells are joined end to end to form phloem and xylem tubes which transport food and water around the plant
• chromosomes contain


  genetic information
• the nucleus contains genetic information in the form of 


  chromosomes
• each chromosome carries 


  a large number of genes
• genes 


  control the development of different characteristics
• body cells


  body cells usually have 2 copies of each chromosome - one from the father and one from the mother
• how many chromosomes are in each body cell

  23 pairs - 46 chromosomes
• why do cells divide

  to increase their cell number in order to grow
• cell cycle


  stages of cell division
• mitosis


  the stage of cell division where the cell divides
• what do organisms use mitosis for

  grow or replace damaged cells
• stages of the cell cycle

  interphase, mitosis and cytokinesis
• stages of mitosis


  Prophase

  Metaphase

  Anaphase

  telophase
• interphase


  genetic information is doubled
• prophase

  centrioles appear
• metaphase


  chromosomes line up in the middle of each cell
• anaphase


  pair of chromosomes separate and are pulled apart to opposite sides of the cell
• telophase


  two nuclei are formed
• cytokinesis


  divides into two new daughter cells
• the end of the cell cycle results in two new cells identical to the original cell with the same number of chromosomes
• before a cell divides

  it increases the number of subcellular structures
• interphase 


  the first stage of the cell cycle, during which the cell grows and replicates its DNA in preparation for division
• what are copied during the initial growth stage and then pulled to opposite ends of the cell?

  chromosomes
• mitosis


  The two sets of chromosomes are pulled to opposite ends of the cell. Then, the nucleus divides into two.