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3: DNA Profiling and Techniques

  • Page ID
    171255
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    • 3.1: ‘Omics Technologies
      Defines a genome as the complete DNA complement of an organism and genomics as large-scale molecular analysis of many genes or whole genomes. Highlights technologies that raise throughput and lower cost.
    • 3.2: DNA Sequencing
      Explains DNA sequencing as determination of nucleotide order in a DNA fragment. Shows how sequence data predict RNA and protein products, inform gene function and relationships, and support studies of gene-expression regulation.
    • 3.3: Whole Genome Sequencing
      Given that the length of a single, individual sequencing read is somewhere between 45bp and 700bp, we are faced with a problem determining the sequence of longer fragments, such as the chromosomes in an entire genome of humans (3 billion bp). Obviously, we need to break the genome into smaller fragments. There are two different strategies for doing this: (1) clone-by-clone sequencing, and (2) whole genome shotgun sequencing.
    • 3.4: Isolating or Detecting a Specific Sequence by PCR
      The Polymerase Chain Reaction (PCR) is a method of DNA replication that is performed in a test tube (i.e. in vitro). Here “polymerase” refers to a DNA polymerase enzyme extracted and purified from bacteria, and “chain reaction” refers to the ability of this technique produce millions of copies of a DNA molecule, by using each newly replicated double helix as a template to synthesize two new DNA double helices. PCR is therefore a very efficient method of amplifying DNA.
    • 3.5: DNA Analysis - Gel Electrophoresis
      A solution of DNA is colorless, and except for being viscous at high concentrations, is visually indistinguishable from water. Therefore, techniques such as gel electrophoresis have been developed to detect and analyze DNA.
    • 3.6: DNA Analysis- Blotting and Hybridization
      Bands of DNA in an electrophoretic gel form only if most of the DNA molecules are of the same size, such as following a PCR reaction, or restriction digestion of a plasmid. In other situations, such as after restriction digestion of chromosomal (genomic) DNA, there will be a large number of variable size fragments in the digest and it will appear as a continuous smear of DNA, rather than distinct bands.


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