The effect of mutations

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  • Mutations
    • Neutral effects
      • An allele is an alternative version of a gene, at the same locus and codes for the same polypeptide
      • If a gene is altered by a change to its base sequence, it becomes an allele of the gene
        • It may produce no change to the organism if:
          • It is in a non coding region of the DNA
          • It is a silent mutation
      • If the mutatuon does cause a change to structure and therefore characteristic, but this gives no disadvantage or advantage then the effect is also neutral
        • Free ear lobes v attached ear lobes - there appears to be no advantage
    • Harmful effects
      • Early humans in Africa almost certainly had dark skin
        • The pigment melanin protected them, but they could still synthesise vitamin D as there was intense sunglight
        • Anyone with a mutation for paler skin would most likely burn and suffer from skin cancer
        • Moving to more temperate climates means that the sunlight was not intense enough for those with darker skin
          • Humans with paler skin would have had an advantage in temperate climates, where their pale skin was a disadvantage in intense climates
    • Beneficial effects
      • Early humans in Africa almost certainly had dark skin
        • The pigment melanin protected them, but they could still synthesise vitamin D as there was intense sunglight
        • Anyone with a mutation for paler skin would most likely burn and suffer from skin cancer
        • Moving to more temperate climates means that the sunlight was not intense enough for those with darker skin
          • Humans with paler skin would have had an advantage in temperate climates, where their pale skin was a disadvantage in intense climates

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