Sunday, January 9, 2011

The Central Dogma

In Biochemistry, the above is known as "The Central Dogma". It used to be the case that we thought RNA, once transcribed as RNA stayed as RNA and that it could never be the case that RNA became DNA. Whether this was the case for reasons of convenience or it was genuinely thought to be impossible, I have no clue, but such a statement does have a "dogmatic" feel to it and so I always took that to be a reason why it was called a Dogma.

The other reason, which is related to it being a central dogma, is that it forms the conceptual basis for a basic biochemical analysis of DNA expression. First one learns what DNA, RNA, and Protein are, and then one learns that this is the general outline by which DNA is expressed into RNA, and the general outline of protein tranlsation from RNA. As has oft been repeated, DNA can be thought of as a code which expresses a sequence of RNA bases, which in turn generates proteins through a well modulated and specific chemical reaction. There are four RNA bases, each of which has a complement on DNA. These four bases form "codons", which are the basis of the genetic code for all life known to date.

A Codon is a sequence with three bases in it. AUG, for example, forms an RNA codon. As there are four bases and three "slots" for each codon, there are 4^3 possible codons, or 64. These 64 possible codons only code for 20 amino acids, which are the building blocks of proteins.

Proteins perform many, many functions within the body, and so understanding how proteins are made and transferred through reproduction forms a strong basis for understanding life at the chemical level. There are many, many details to get lost in, and some of the nitty-gritty details are really only known by people in that specific research field. This is why the central dogma is of so much importance: It gives a foundational biochemical reference point to which we can connect all of our other knowledge to.

I said earlier that it used to be thought that DNA makes RNA, end of story. That, now, has changed -- it turns out that we've found enzymes which help to reintegrate RNA back into DNA sequences. This enzyme is called "reverse transcriptase", and it is through mechanisms such as these that viruses infect us. Although, to them, it's not an infection: It's their method of reproducing themselves. A greater understanding of this purely theoretical mechanism can yield practical results in the field of AIDS treatment, which goes to show how a general theoretical question like ,"How does a cell operate at the chemical level?" can possibly lead to practical benefits. Surely this isn't the motivation behind such research, as such research is intrinsically interesting, but it does go to show how intrinsically interesting questions which have no perceived benefit are often connected to practical benefits.

The other thing that the central dogma shows is that even scientific "dogma" can undergo revision. As far as I can tell, whether it was for heuristical reasons or judged to be this way, the central dogma was taken very seriously. Yet, over time, we've had to revise our models given a long series of inquisitive arguments. It can't be emphasized enough that even our most basic scientific descriptions are taken as fallible constructions -- not to dissuade persons from the credibility of scientific work, but to make persons aware of how far a scientific argument can go. The word "science" has often been used to legitimize, and pointing out how actual science is full of qualifiers -- like "may", "could be", "might", "I suspect", coupled with complex arguments from difficult to obtain and possibly faulty data to likely rejectable conclusions, at least in so far as it's only a published paper -- can only help the public to critically evaluate scientific claims.

Or, in short, even the most stalwart of scientific constructs have hesitancy involved: If a company or politician may gain by your acceptance of their scientific claims, and they lack this hesitancy, you might want to turn your bologna alarm on and check some alternate sources.

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