Cell Division

Information on the two types of cell division: 

Mitosis

Meiosis

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  • Created by: jenny100
  • Created on: 15-05-12 00:24

DNA - Background Information

  • Found in the nucleus of animal and plant cells
  • Made up of really long molecules called chromosomes
  • A gene is a section of DNA, it contains the instructions to make specific protein
  • Cells make proteins by stringing amino acids together in a certain order
  • DNA determines what proteins the cell produces which in turn determines what type of cell it is, e.g. haemoglobin --> red blood cell 
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Mitosis

Mitosis makes new cells for growth and repair and it is when a cell reproduces itself by splitting to form two identical offspring

  • Body cells have two copies of each chromosome (one from the mother and one from the father)
  • Human body cells have 46 chromosomes and gametes have 23 so when the male & female gamete combine you get 46 chromosomes again
  • DNA is copied and forms X-shaped chromosomes each 'arm' the exact copy of the other
  • Chromosomes then line up in the middle of the cell and cell fibres pull them apart
  • Membrane forms around each set of chromosomes, these become the nuclei of the two new cells
  • Then the cytoplasm divides and two new identical cells are formed

Asexual reproduction also uses mitosis, the offspring have no variation because they have the same genes


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Meiosis

Meiosis produces cells with only half the normal number of chromosomes

  • As with mitosis ty DNA duplicates and in the first division the chromosomes pairs are lined up in the centre of the cell
  • The pairs are pulled apart so each new cell only has one copy of each chromosome
  • Each new cell has a mixture of the mother's and the father's chromosomes, this creates variation on the offspring
  • In the second division the chromosomes line up again and the arms are pulled apart 
  • Now you get four gametes with only a single set of chromosomes in it 
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