Chromosomes and mitosis :

• • The nucleus of a cell contains chromosomes
• Each chromosomes carries a large number of genes
• Different genes control different characteristics e.g hair colour
• Body cells normally have two copies of each Chromosomes
• The cell cycle makes new cells :

  • Body cells in multicellular organisms divide to make new cells in part of a series or stages called the cell cycle
  • The stage of the cell cycle when a cell divides is called mitosis
  • Multicellular organisms use mitosis to grow and develop
• What is Mitosis ?

  • Mitosis is when a Cell divides once , to form two new identical cells
• process of Mitosis ( more detailed )

  1. First the Cell grows and increases the amount subcellular structures like ribosomes and mitochondria
  2. Then the DNA is replicated and forms an X shaped chromosome
  3. The chromosomes then lineup on the centre of the cell where two arms of each chromosome are pulled apart to opposite end of the cell
  4. Then this divides the nucleus where each set of chromosomes becomes the nucleus of new cell
  5. The cytoplasm and Cell membrane, then divide to produce Two new cells that contain the same DNA and is identical to the original cell
• How many chromosomes are there in a human cell?

  • There are 46 chromosomes in a human cell
• What are chromosomes?

  • Chromosomes are coiled up lengths of DNA molecules and contain genetic information
• What is the process of mitosis?

  1. DNA duplicates and grows
  2. Chromosomes lineup in the centre and spindle fibres pull them apart
  3. Nuclei reforms and cell membrane and cytoplasm splits
  4. Two daughter cells are formed