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Porphyria Educational Services Weekly Bulletin  
Vol. 2 No. 46                                         November 19, 2000
     
FOCUS:  GENOMICS
 

As we ponder the future for a cure for porphyria we read all kinds of
reports on gene therapy, DNA, and the human genome.  So what does it all mean?   The now famous "human genome project," was recently completed during this millenium year.The human genome project completed in 2000, was completed five years ahead of schedule.

 So just exactly what was this project and how does it directly
affect a porphyric?     The human genome project was a monumental project wahich was undertaken to decode the entire DNA sequence of a human being....a human being like you or I.  This "sequence" as it is called, is precisely known as the human genome.      When you ponder your body and look at your flesh, you canonly begin to understand how large an undertaking this project was in reality.  It was very large.   Looking at your flesh you see a pattern in the skin made up of  thousands of human cells. Each human cell contains 46 chromosones.  Each one of these is a DNA molecule. Each DNA molecule is wrapped around proteins which are scientifically known as histones.   It has been fairly well estimated that if all of the DNA molecules in one cell were unwrapped from the histones and these molecules were stretched out end-to-end, the total length would be about six feet in length.   To go further, it is estimated that almost every cell in your entire body contains six feet of DNA.  Each cell containing DNA is wrapped up into a very small compact space.   One scientific report has stated that if one were to print out all of the information in the human genome, such a project would fill over a thousand  large sized telephone directories. From this comparison one can clearly visualize the vastness of the DNA of the human body.   The entire sequence of the human body contains about three billion base pairs.  And just what are base pairs?  The base pairs are like alphabet letters  but are used in genetics. These genetic alphabets include over 50,000 - 100,000 genes.  For each of these there are specific codes for each protein.   Porphyria patients who have been DNA tested and mapped can identify the specific gene that has mutated and is defective in the heme pathway.  It is precisely this defective gene that causes the maladies that are exhibited by the type of porphyria  one has. The codes that are used are each for a specific protein.   Each type of porphyria affects a given chromosone, and gene.  Mutations of such can also cause subtypes within one type of porphyria.  Each generation of a family lineage will also show variances and changes in the mutations.  This is especially true is two individuals with different inherited metabolic defects marry and produce offspring.  This is thought to account  somewhat for photo sensitivity  occurring in more and more AIP type porphyria patients, where previously AIP patients did not experience photosensitivity.   Dr. Gerald Lawrence, MD, PhD