sequencing the genome

  • Created by: vezting
  • Created on: 23-02-16 17:30
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  • sequencing gene and genomes
    • DNA sequencing
      • 1: this mixture is split into 4 test tubves
        • single-stranded DNA template to be sequenced
        • DNA polymerrase to join nucleotides together
        • lots of DNA primer
        • many free floating nucleotides
        • a fluorescenty labelled modified nucliotide, after attaching to DNA strand, no more nucleotides attach after it.
      • 2: tubes undergo PCR. the strands are different lengths as they terminate at different points
      • 3:DNA fragments in each tube seperated by gel electrophoresis and visualised under UV light because of fluorescent label.
      • 4: smallest nucleotide (1) is at the bottom of the gel, each band after this represents one nucleotide added, so reading upwards you can get the sequence
    • genome sequencing
      • chain termination method (DNA sequencing) can only be used for fragmetns up to 750bp long
        • to sequence whole genome it needs to be chopped into smaller bits then put back together
      • 1: genome cut into 100,000 bp long peices using restriction enzymes
      • 2: fragments inserted into BACs
      • 3: BACs inserted into bacteria
      • 4: bacteria divide, creating colonies of cloned cells which all contain specific DNA, making a genomic DNA library
      • 5: DNA is extracted from each colony and cut using restriction enzymesproducing overlapping peices of DNA
      • 6: each peice of DNA is sequenced using chain termination method.
      • 7: the peices are put back in order to give full sequence from that BAC, then DNA fragments from all BACs are put in order for entire genome
    • comparing genomes
      • we want to compare between different species to help us understand evolutionary relationships
        • closely related species will share more DNA than those less closely related
          • comparing across species help us understand how genes react during development and how theyre controlled
      • comparing genome within species helps trace early human migration
        • is also used to study human genetic diseases
        • sciensits also compare within species to develop medical treatmentments for particular genotypes


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