• Chromosomes found in the nucleus of cells 
  • Chromosomes are long lengths of coiled DNA
  • Small sections of DNA are called genes which code for proteins
  • Proteins control processes in the body they also determine inherited characteristics
  • Different versions of the same gene are called alleles 
  • DNA is a double helix, it has a sugar phosphate backbone 
  • It has four bases A(adenine), T(thymine), C(cytosine), G(guanine)
  • A pairs with T
  • G pairs with C -this is complimentary base pairing
  • Bases are held together with hydrogen bonds
  • DNA is a type of nucleic acid
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  • Type of asexual reproduction
  • New cells made are genetically identical to the parent cells
  • Cells are diploid- Cells have pairs of chromosomes (46)
  • Stage 1-The Chromosomes duplicate and the nuclear membrane breaks down 
  • Stage 2-The Chromosomes line up along the centre of the cell 
  • Stage 3-Spindle fibres (cell fibres) pull the chromosomes to opposite ends
  • Stage 4-Membrane form around the chromosomes to form nuclei
  • Stage 5-The Cytoplasm divides 
  • Stage 6-Two newdaughter cells are produced
  • Mitosis in needed for growth of plants and animals and repair of worn out or damaged tissue
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  • Sexual Reproduction-leads to genetic variation
  • Happens in the gametes (sperm and egg)
  • Gametes are Haploid-only has single chromosomes (23)
  • At fertilisation gametes fuse to form a zygote with a full set of chromosomes (46)
  • Stage 1-Chromosomes duplicate and nuclear membrane breaks down
  • Stage 2-Chromosomes line up along the centre, crossing over of chromosomes happens (exchanging sections of chromosomes) and chromosomes get pulled apart to each end of the cell
  • Stage 3-The Cytoplasm divides
  • Stage 4-The Chromosomes line up again and are pulled apart to each end of the cell 
  • Stage 5-The Cytoplasm splits
  • Stage 6-The Nuclear membrane forms and 4 new cells are formed and these are haploid

All four cells are genetically different to eachother

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