Genetic diagrams


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  • Genetic diagrams
    • Genetic diagrams show the possible genes of offspring
      • 1) Different genes control the development of characteristics e.g. eye colour
      • 2) There can be different versions of the same gene. These are called ALLELES
      • 3) These alleles give different versions of a characteristics, E.g blue eyes or brown eyes
      • 4) You have two alleles for each gene
      • 5) Alleles can be dominant or recessive
      • 6) If you have two dominant alleles, the dominant characteristic will be shown
      • 7) If you have one dominant and one recessive allele, only the dominant characteristic will be shown
      • 8) To show a recessive characteristic, both alleles for a gene have to be recessive
    • You need to use and understand genetic diagrams
      • 1) Imagine you are cross breeding hamsters, and that some behave normally while others do some crazy acrobatics
      • 2) Let's say that the allele which causes the crazy behaviour is recessive- so use a 'h'
      • 3) and normal behaviour is due to the dominant gene 'H'
      • 4) so a crazy hamster must have the alleles 'hh'
      • 5) but a normal hamster could be 'HH' or 'Hh'
      • 6) There's a 75% chance of having a normal hamster, and 25% chance of a crazy one
        • This gives a 3:1 ratio of normal:crazy offspring


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