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