First the DNA is Amplified

  Before sequencing, strands of DNA are first amplified, usually by PCR (polymerase chain reaction).  PCR is a process that uses a special polymerase enzyme that synthesizes a complementary strand of DNA to any given strand.  The mixture of polymerase, DNA, primers and bases is heated so that the DNA will split apart, then cooled so the enzyme can work.  When this round of replication is through, the process is repeated, adding more polymerase and bases as need, until sufficient quantities of DNA have been produced.
 
  
Then it’s Sequenced
  
  DNA is currently sequenced by one of two methods:  the Maxam-Gilbert method (aka the chemical degradation method) and the Sanger method (aka chain-termination method, dideoxy sequencing).  In the Maxam-Gilbert method, the DNA is cut apart at specific bases, resulting in fragments of different lengths.  In the Sanger method, DNA is replicated in the presence of an abnormal base that can only link to one other base, as well as the four normal bases.  When an abnormal base binds to one end of the growing strand of DNA, the chain ends there.  Like the Maxam-Gilbert method, this produces fragments of DNA of different lengths.  The fragments (from either method) undergo gel electrophoresis to separate them by length, and computers are used to analyze and assemble the base sequence.  Most of this process is, in fact, automated.

  More advance and efficient techniques, some of which don’t even involve gel electrophoresis, are being developed now.  In the future DNA may be sequenced through mass-spectrometry or read directly with a scanning tunneling microscope.

  And remember, you may not know how genes will be found in the future, but you’ll always know where to find them….at GENESnow.com—your genes, your store, for today and tomorrow!!

Outside Links

 --http://www.bis.med.jhmi.edu/Dan/DOE/prim6.html
 --http://www.niehs.nih.gov/envgenom/glossary.htm
 --http://www.vmmc.org/vmrc/genotype/contents.htm
 --http://www.ibc.wustl.edu/SNP/ 
 --http://www.ncbi.nlm.nih.gov/SNP/
 --http://www.ornl.gov/TechResources/Human_Genome/publicat/hgn/v7n6/09detect.html
 --http://www.vmmc.org/vmrc/genotype/sscp.htm