Transcription is the process from poly-nucleotide to
poly-nucleotide (for example DNA to mRNA).
Translation is the process from poly-nucleotide to
poly-peptide or protein or amino-acid string.
(for example mRNA to protein)
the reading frame is defined as follows: (one can consult a
biochemistry book for more details).
Each amino acid is coded by a nucleotide triplet.
mRNA consists of a polymer that consists of a sequence of
the nucleotides Uracil, Cytosine, Adenine, and Guanine.
These are abbreviated U,C,A, and G.
Consider the following example:
mRNA ...UGUCAUGCUGUGGC...
It takes three nucleotides to translate into an amino acid.
Depending on where you start the translation process, you
can get completely different amino-acid strings (or proteins).
For example, if you start at the beginning of the above
section of mRNA you will get the following:
mRNA ..-UGU-CAU-GCU-GUG-GC...
protein ..-cys-his-ala-val-
starting at the second position, one gets
mRNA ..U-GUC-AUG-CUG-UGG-C...
protein ..-val-met-leu-trp-..
Starting at the third position, one gets
mRNA ..UG-UCA-UGC-UGU-GGC-...
protein ..-leu-cys-cys-gly-..
The lower-case triplets refer to three letter
abreviations of amino acids. For example, cys is an
abreviation for the amino acid cystein.
Note that there is some redundancy in the genetic code.
For example UGC and UGU both code for cys.
The point is the following: If you start in a different
place (a different reading frame), you get a completely
different protein. And if it is functionally active (not
just nonsense) it will probably be functionally different.
Therefor the same piece of genetic code can code for
different functions.
It is dogma in biochemistry that the reading frame is built
into the genetic code itself...so that there is only one
reading frame. There is a certain start sequence (AUG)
that establishes the reading frame.
Kampis, I think, is challenging this dogma and suggesting
that the reading frame can shift depending on context...
the context being determined both by previously translated
proteins and environmental input.
He did not elaborate a lot on how this occurs in his article.
I think Hans-Cees was suggesting that this change in reading
frame could only occur by mutation. Im very interested in
finding out if Kampis is thinking of non-mutational ways in
which the reading frame can change.
Jeff Prideaux