Re: Prion and Central Dogma

This is a strong question Berenice.

     One of the beauties of science is that quite often what is considered

absolute fact turns out to be not much more than a good suggestion, waiting

to modified or even disproven.  The Central Dogma (which somebody has made

a picture of here) is one of those rules that has had to be modified

in recent years, mainly because the dicovery of infectious diseases (such as

viruses and prions) that appear to violate it.  

     It was discovered in the mid 70's that retroviruses (such as HIV) have an

enzyme called reverse trancriptase that can make DNA from RNA, reversing the

Dogma.  In the early to mid 80's a group of RNA molecules called ribozymes

were found to behave like protein enzymes, changing themselves as well as

other RNA molecules.  Now, these prions are thought to reproduce themselves 

without the help of any nucleic acid, although there are still some weakening

arguements against that hypothesis.  

     It also appears that prions are found not only in cattle and humans, but

also in simple organisms such as yeast, where they might even be advantageous

to the yeast rather than disease causing.  So I'd have to agree with your

statement Berenice, yet another Dogma buster.  Thanks for your question.



Michael Crawford