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  • Inheritance
    • There are many different genetic disorders.
      • Some are caused by a dominant allele, some recessive.
        • If the allele is dominant the person only has to inherit only 1 dominant allele to have the disorder.
          • An example of a disorder is polydactyly.
            • If an allele is recessive the person must inherit 2 recessive alleles to have the disorder.
        • Cystic fibrosis is caused by a recessive allele.
          • The allele affects cell membranes and causes the production of thick sticky mucus. The mucus can affect several organs, including the lungs and pancreas.
            • A child must inherit a recessive allele from both parents to develop cystic fibrosis.
              • The disorder can be passed on from 2 parents who don't have cystic fibrosis, they have to be carriers of the allele.
    • Genetic Diagrams
      • By using genetic diagrams it is possible to see how a disorder has been inherited and also to predict whether future offspring will inherit it.
      • Homozygous- Both alleles are the same, DD (homozygous dominant) or dd (homozygous recessive)
      • An organism can also be Hetrozygous this means that it has two different alleles.
    • Humans have 23 pairs of chromosomes one of these are the sex chromosomes. Females have 2 X's and Males have a X and a Y.
      • Genes controlling the same characteristics are called alleles. If an allele masks the effect of another it is dominant, if it is being masked then it is recessive.
        • A phenotype is the physical appearance of the characteristic
          • A genotype is the genetic make up which alleles does the indervidual inherit? DD, Dd or dd
  • DNA
    • Genes are found on chromosomes
      • Chromosomes are made of DNA which is a very long molecule with a double Helix
        • Genes are short sections of DNA.
          • Every individual has different DNA.


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