Mutations, Genetics Disorders and Cancers

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  • Created by: Sophie
  • Created on: 06-04-15 09:32
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  • Mutations, Genetic Disorders and Cancer
    • Mutations are changes in the base sequence of DNA
      • Can be caused by errors in DNA replication
      • Can be caused by mutagenic agents
      • Types of errors:
        • Substitution: One base is substituted for another
        • Deletion: One base is deleted
      • Different order of AAs, different protein formed.
    • Not all mutations affect the order of AAs
      • Degenerate nature of DNA means some AAs are coded for by more than 1 triplet
      • Not all substitution mutations change the AA sequence
      • Deletion always changes AA sequence
        • Change in number of bases present, causing shift in base triplets after it
    • Mutagenic Agents Increase the rate of mutation
      • Mutations occur spontaneously
      • Ultraviolet radiation, ionising radiation, some chemicals and some viruses are e.g.s
      • Increase rate of mutation by...
        • Acting as a base: chemicals called base analogs substitute for a base in replication.
        • Altering bases: Some chemicals can delete or alter bases.
          • E.g alkylating agents, add alkly group, changing structure so it pairs with something different.
        • Changing the structure of DNA: Some radiation changes structure of DNA, causing problems in replication
    • Genetic disorders and cancer are caused by mutation
      • Hereditary mutations cause genetic disorders and some cancers
      • Inherited disorders caused by abnormal genes or chromosomes
        • If a gamete containing the mutation for a genetic disorder is fertilised, the fetus will have the disorder
      • Some mutations increase the likelihood of developing cancers
      • Acquired mutations can cause cancer
        • Mutations that occur in individual cells after fertilisation
        • If these mutations occur in the genes that control cell division, you may get a tumour
          • A mass of abnormal cells
          • Cancerous tumours invade and destroy surrounding cells
        • 2 types of gene controlling cell division
          • Tumour suppressor genes
            • Tumour suppressor genes can be inactivated if a mutation occurs in the DNA sequence
              • If a mutation occurs, the protein isn't produced. The cells divide uncontrollably.
            • When functioning normally, tumour suppressor genes slow cell division by producing proteins that stop cells dividing or cause them to self destruct
          • Proto-oncogenes
            • If a mutation occurs in the DNA sequence, the effect of a proto-oncogene can be increased
              • Oncogene produced
              • When functioning normally, proto-oncogenes stimulate cell division by producing proteins that make cells divide
              • If a mutation occurs, the gene cam become overactive, stimulating cells to divide uncontrollably resulting in a tumour


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