Studying genomes

  • Created by: Steff06
  • Created on: 13-05-16 12:24
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  • Studying genomes
    • Methods:
      • Genome sequencing + comparative genome mapping.
      • Genetic fingerprinting
      • Gene therapy.
      • Genetic engineering.
    • Natural processes:
      • DNA cut into smaller fragments using restriction endonuclease
      • Fragments separated using electrophoresis.
      • Replicated many times by polymerase chain reaction (PCR).
      • DNA fragments analysed to give specific base sequence.
      • DNA fragments sealed together using DNA ligase.
      • DNA probes used to locate specific sequences on fragments.
    • Genomic age:
      • Genes code for proteins and polypeptides.
      • This coding DNA forms a small part of DNA. Most is non-coding DNA.
    • Sequencing can only operate on 750 base pairs so genome must be broken up and sequenced in sections.
    • Genomes mapped. Known info e.g. location of microsatellites used.
      • Samples of genes sheared into smaller sections of 100,000 base pairs (shotgun approach).
        • Sections put in separate Bacterial Artificial Chromosomes (BAC's). Transferred to E.coli cells.
    • Sequencing a BAC section:
      • 1. Cells with specific BAC's taken and cultured. DNA extracted and restriction endonucleases used to cut into smaller fragments.
        • Different restriction enzymes used to produce different fragment types.
      • 2. Fragments separated by electrophoresis.
      • 3. Each fragment sequenced using automated process.
      • 4. Programmes compare overlapping regions from cuts made by different restriction endonucleases.
        • Done to reassemble whole BAC segment sequence.
    • Comparing genomes:
      • Comparing sequences across range of organisms = Comparative base mapping
      • Applications to identification of genes in proteins and their importance.
      • Can compare DNA of different species to show evolutionary relationships.
      • Modelling effects of changes of DNA.
      • Comparing genomes from pathogenic and similar non-pathogenic organisms.
      • DNA of individuals analysed to reveal mutant alleles or increased risk of disease.


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