Those two sections are called Introns and Exons.  Introns are generically non-coding (appear non-functional) strands of DNA.  When mRNA and tRNA are created the Introns are excluded, so they contain only the Exons.  The Exons are the coding strands as they contain the genes that govern our alleles.  It was once generally assumed that the Introns served no purpose.  However recent research has shown they have a purpose, but no one is really sure what that is (or was...).  A couple of theories are floating around about how they could exist to preserve the structure and shape of the DNA molecule and aid in its folding, or they could be remnants of when we were wee little prokaryotes.  They are known to contain lots of old information as well that, as far as we can tell, is there because...well...it hasn't gone yet.

Introns also contain old DNA from vestigial organs or processes as well as some ancient viruses.  I truly wish I remembered the statistic from my text book but it is estimated that every human has several hundred old viruses embedded in his or her DNA that is simply inactivated due to some mutation or the machinery it used is gone or some other reason.  Truly fascinating stuff.

It is technically possible for a mutation to reactivate it insofar as if a mutation happened at that exact point of a mutation that deactivated it, or an old virus that existed received a mutation which changed how it worked and brought it out of dormancy  Of course the odds are quite long but they are still there, hence the risks associated with inserting random mammalian or another animal genes into crops: we do not know for sure how they will react with our current genes OR our old ones.  

To Chem,

I agree with you in that it is foolish to press out a science because of fear.  However, precautions should be taken.  In that case where the GM crop was outclassed by its origin I believe the GM crop WAS meant to be a hardier species and the test was in a more nominal environment so in that conclusion the study was a bit...disingenuous.  However, the company was at fault as well because they themselves marketed their seed as superior in all environments.  Both sides had an agenda.  I for one would like to see it redone in the environment the seed was originally designed for.

In any case, even with 50 years of research one still cannot dismiss the risk.  If biology and my familial history riddled with cancer (my wifes side mostly, but my side is not immune) has taught me one thing, its that every single person is unique.  Medicine, sickness, and potential disease react differently in large part to their genetics.  Many drugs and diseases are specific to particular cells, proteins, and other compounds in the body.  One, tiny, seemingly insignificant change can mean the difference between a nasty bought of the flu and a day long runny nose.  Sure, 50 years sounds like a lot, but with each new little meddle of the genetic code of a product introduces another potential aggressor.  Its not just that one thing as well, it could interact with previous changes and modifications that were once previously harmless.  Thus, we are caught in a bit of a bind.  I don't think any amount of testing will truly be able to say that, %100 of the time a specific GM crop will result in a negative consequence small or large because the scope of human genetic variation is so great.  What must be determined is what degree of risk are we willing to accept?  

GM crops can, and I am sure that they will eventually, serve an extremely valuable purpose in providing efficient food-crops to otherwise poor or non arable land.  If one is facing starvation in the short term or undetermined genetic consequences in the long-term than I for one would eat the food and deal with the consequences.  This point however should still be after significant testing.  Plants are resilient, cross pollination is shockingly easy, and man-kind has always been good at mating and propagating genes, good or bad.  It would be unwise of us to make these plants willy nilly with little discipline and propagate something which puts the entire race at risk due to damage to our food supply.  Mother nature dislikes being under control and will rebel given the slightest space.  

I get over excited when I get to talk about things related to my profession and my typing goes down hill.  

On a related note: a quick google search trying to find some examples of ancient viruses affecting us today came up with a study in 2004 which found that the onset of multiple sclerosis could be assisted by a vulnerability created by an ancient virus embedded in our DNA.  

I agree science with out discipline can only lead to disaster, and there is now way to be 100% sure, a margin of error must be left. But the thing with genetic mutation occurring in a negative way can seem to happen without anything new added to the system, I am the first in my family to have a server nut allergy, although I also carry my grandfathers allergy towards penicillin. I'm sure if we looked hard enough we could find the root cause. Adding something new to this giant equation probably wont help matters like you said, as a chemist we only look at the individual amino acids or side chains thus we have a narrow view, so I adhere to you knowledge of the subject. I'm sure this is being done but if we study animals such as mice, who are able to produce multiple generations in a short time we should be able to spot inherent genetic if defects.

Its quite possible to determine the effects and side effects.  The problem is the sheer scope and size of the genome.  It just takes a LOT of work.  Plus, especially with how technical genetics is, you have to study a broad subject from a narrow view of individual chains and side molecules and then extrapolate those results to the larger picture.  The time consuming part of this is that until you study an individual gene extensively you simply don't know what it creates and what all it is involved in so, in a sense, its like putting together a blank puzzle that won't show a picture until its finished or one section is complete.  Sure, the pieces might fit, but you dont know if the picture makes sense until you can see the entire system. 

 

I know in Cancer Biology there is a gene, I think its P53, but I could be wrong as its been a while, that was once thought to cause cancer.  It is now known to actually play a huge role in preventing cancer.  When mutations in this gene cause it to be non-functional or change its function it makes it much easier for cancer to grow.  With P53 though is a network of at least 4 other genes that serve in related functions with controlled cell death (apoptosis) , replication, cell aging, etc.  It took us a while to figure this all out because with each new gene we discovered and researched our grand picture we thought existed changed.  Its a truly fascinating subject.  Will we achieve a point where we could reasonably accurately predict or determine what would be a long-range genetic threat?  I certainly think so, it will just take a long time. 

Because the TV tells you so.

For instance the only accurate description of the what happened at Tsernobil I've read was in a physics book, not a newspaper and not on TV.

Wolfson and Pasachoff, Physics with Modern Physics for Scientists
and Engineers, 2 ^nd ed.


ISBN 0-06-501016-7

Pages 1200 and 1201