Chromosomes and Mitosis

• Chromosomes


  Coiled up lengths of DNA molecules that contain genetic information
• Chromosomes

  • Each chromosome contains a number of genes that control the development of different characteristics
  • Body cells normally have two copies of each chromosome, one from the mother and one from the father
• The diagram shows the 23 pairs of chromosomes from a human cell
• Cell cycle


  A series of stages that body cells in multicellular organisms go through to divide and produce new cells for growth, development and repair
• Mitosis


  The stage of the cell cycle when the cell divides
• Mitosis


  • Multicellular organisms use mitosis to grow or replace cells that have been damaged
  • The end of the cell cycle results in two new cells identical to the original cell with the same number of chromosomes
• Growth & DNA Replication

  1. DNA is all spread out in long strings

  2. Cell grows and increases subcellular structures

  3. Cell duplicates its DNA to form X-shaped chromosomes with identical arms
• Mitosis


  1. Chromosomes line up at the centre of the cell

  2. Cell fibres pull the chromosomes apart, with the two arms going to opposite ends

  3. Membranes form around each set of chromosomes to become the nuclei of the two new cells

  4. Cytoplasm and cell membrane divide to produce the two new daughter cells
• The daughter cells contain exactly the same DNA as the parent cell, they are identical