Chromosomes and Mitosis

Chromosomes contain genetic information:

• The nucleus of a cell contains chromosomes
• Chromosomes are coiled up lenghts of DNA molecules
• Each chromosome carries a large number of genes
• Different genes control the development of different chracteristics, e.g hair colour
• Body cells normally have two copies of each chromosome
• There are 23 pairs of chromosomes in a human cell

The cell cycle makes new cells:

• Body cells in multicellular organisms divide to make new cells
• The stage of the cell cycle when the cell divides is called mitosis
• Multicellular organisms use mitosis to grow and develop

DNA replication:

• The cell grows and increases the amount of subcellular structures such as ribosomes and mitochondria
• The DNA is replicated (copied) so there's one copy for each new cell
• The DNA forms X-shaped chromosomes.

Mitosis:

• The chromosomes line up at the centre of the cell.
• The two arms of each chromosome are pulled apart to opposite ends of the cell.
• This divides the nucleus
• Each set of chromosomes become the nucleus of a new cell
• The cytoplasm and cell membrane divide.
• THE CELL HAS NOW PRODUCED TWO NEW CELLS WITH THE SAME DNA.