DNA Profiling

Summary of DNA Profiling and the cycle used to create a profile 

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  • DNA Profiling
    • Why?
      • Screen for a genetic condition
      • Measuring genetic diversity
      • Studying Evolutionary relationships
    • How?
      • STRs occur at the same loci on both homologous chromosomes
      • Looks at the introns. WIthin introns  STR are found
      • Number of STRs vary between individuals
    • Obtaining the DNA
      • Cells from cheek swap, blood, tissue, bone marrow
      • Sample broken down in detergent
      • DNA extracted from cell debris by filtering or certrifuging
        • Protease enzymes added to remove proteins
      • Cold ethanol to precipitate out the DNA
    • Creating the Fragments
      • Restriction enzymes / endonucleases wil cut DNA at specific bases
        • Found naturally in bacteria where they cut up viral RNA
        • Same restriction enzyme is used  to cut two identical DNA samples, identical STR fragments will be created
    • Polymerase Chain Reaction
      • DNA is copied numerous times
      • DNA Primers = short sections of DNA complementary to the DNA adjacent to the STR
      • DNA primers, nucleotides, DNA polymerase added to reaction tube
    • Gel electrophreisis - Separating Strand
      • Connected to electrodes, negatively charged DNA travels to the positive electrode
      • DNA fragments add to agrose gell which is submerged into buffer solution
    • Visualising the Fragments
      • Technique called southern blotting, nirtocellulose membrane placed directly on the gel and a wad of dry paper is placed on top
      • Single band occurs on a profile when a persons maternal and paternal chromosomes have same number of repeats at a particular locus


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