Science // Biology // B1 // Variation and Mutation //

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  • Genetics and DNA
    • Continuous variation
      • Small differences between individuals
      • Greatly affected by environment
      • e.g heigh, shoe size, length of hair plotted on a line graph
    • Discontinuous vartiation
      • Differences that are classed or categorised
      • Not greatly affected by environment
      • E.g Blood group, sex, hair colour, eye colour plotted on a bar chat or pie char
    • Environmental variation
      • Environment affects how our inherited characteristics develop
        • For example growing up in different areas can affect acents, and being somewhere sunny can affect your skin tone.
    • Genetic variation
      • Causes;
        • Mixing of parent information during meiosis
        • Gamete forms from a unique combination of genetic information
      • Siblings can have both similar and different traits.
      • e.g having a mixture of their parents characteristics, fathers eyes, mother's hair.
    • Mutation
      • During replication, an organism's gentic DNA can change or mutate. Changes to genes are called mutations.
        • Mutations just happen, this happens because of radiation and chemicals such as tar.
          • If mutation is large then the organism will probably not survive to reproduce.
            • If a mutation is small then change may be beneficial. Offspring will flourish, doing betr than others in that species. More offspring will inherit this beneficial mutation and will be better suited to that envirnoment
              • Mutations may have no effect, for example th protien that a mutated gene produces may work just as well as the protein from the non-mutated gene.
                • Yet mutations can be helpful yet harmful. For example haemophillia is an inherited disorder hat stops blood clotting properly. It is caused by a mutated gene.
  • This continues natural selection
    • If mutation is large then the organism will probably not survive to reproduce.
      • If a mutation is small then change may be beneficial. Offspring will flourish, doing betr than others in that species. More offspring will inherit this beneficial mutation and will be better suited to that envirnoment
        • Mutations may have no effect, for example th protien that a mutated gene produces may work just as well as the protein from the non-mutated gene.
          • Yet mutations can be helpful yet harmful. For example haemophillia is an inherited disorder hat stops blood clotting properly. It is caused by a mutated gene.
    • Genes can be switched on and off

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