There are a lot of great resources available on the internet for countering Code Denialism. I’ve gathered a few of them for your convenience. I envision a multi-part series on this topic because the evidence against Code Denialism is so extensive and Code Denialism seems to be surging in popularity here at TSZ.
The 1961 paper by Crick et al. is an outstanding example of the use of thought and logic to solve basic biological problems. In my opinion, it is a superb paper to assign to students in courses because it illustrates how combining knowledge and wisdom can provide answers to important scientific questions.
They demonstrated that three bases of DNA code for one amino acid in the genetic code. The experiment elucidated the nature of gene expression and frame-shift mutations.
…the mutant strains could be made functional again by using proflavin to insert or delete a total of three nucleotides. This proved that the genetic code uses a codon of three DNA bases that corresponds to an amino acid.
“This concept of a phase shift, or a ‘frameshift’ [in the genetic code of an rII gene] as we later called it, was so foreign to people in genetics that we had endless problems trying to explain this work.”
Seems like they still have work to do.
The famous paper:
THERE is now a mass of indirect evidence which suggests that the amino-acid sequence along the polypeptids chain of a protein is determined by the sequence of the bases along some particular part of the nucleic acid of the genetic material. Since there are twenty common amino-acids found throughout Nature, but only four common bases, it has often been surmised that the sequence of the four bases is in some way a code for the sequence of the amino-acids. In this article we report genetic experiments which, together with the work of others, suggest that
the genetic code is of the following general type:
(a) A group of three bases (or, less likely, a multiple of three bases) codes one amino-acid.
(b) The code is not of the overlapping type.
(c) The sequence of the bases is read from a fixed starting point. This determines how the long sequences of bases are to be correctly read off as triplets. There are no special `commas’ to show how to select the right triplets. If the starting point is displaced by one base, then the reading into triplets is displaced, and thus becomes incorrect.
(d) The code is probably `degenerate’; that is, in general, one particular ammo-acid can be coded by one of several triplets of bases.
Is the Code Degenerate?
… the code is probably `degenerate’, that is, in general more than one triplet codes for each amino-acid. It is well known that if this were so, one could also account for the major dilemma of the coding problem, namely, that while the bese composition of the DNA can be very different in different micro-organisms, the amino-acid composition of their proteins only changes by a moderate amount.
The Nobel Lecture:
I shall discuss here the present state of a related problem in information transfer in living material – that of the genetic code – which has long interested me, and on which my colleagues and I, among many others, have recently been doing some experimental work.
…It is convenient to have a word for a set of bases which codes one amino acid and I shall use the word “codon” for this.
…There is nothing in the backbone of the nucleic acid, which is perfectly regular, to show us how to group the bases into codons. If, for example, all the codons are triplets, then in addition to the correct reading of the message, there are two incorrect readings which we shall obtain if we do not start the grouping into sets of three at the right place.
In spite of the uncertainty of much of the experimental data there are certain codes which have been suggested in the past which we can now reject with some degree of confidence.
Message, messenger, or genetic message appears 12 times. Other codes were proposed and rejected.
The genetic code is a code.
The evidence against Code Denialism is overwhelming.
There’s really nothing to discuss. But if you insist…