The code of real DNA consists of 64 combinations of "codons", which are groupings of 3 "nucleotide" molecules of which there are 4 varieties. These are symbolized by T, C, A, and G, the first letters of their chemical names. These 64 combinations (TTT, TTC, TTA ... GGA, GGG) code for the 20 amino acids that make up all proteins. As there are more than 3 times as many combinations than are minimally needed to code for the amino acids, there is quite a bit of redundancy in the code, with in one case 6 different combinations coding for the same amino acid. (This is a protective feature.) There are also 2 combinations that indicate a specific gene is beginning and 3 that indicate its end (within the very much longer "double helix" chains of DNA).
While this elegant system is amazing in itself, what really boggles the mind is that some genes can code for more than one protein at the same time. In order to accomplish this amazing feat, information stored somewhere else in the DNA directs certain small sections of the reading frame (called introns) to be spliced out when the encoded information is being transferred to the messenger RNA molecule to deliver the instructions to the protein manufacturing sites in the cell. For instance, if a section of nucleotides in the chain (that are not identical with a set of codons) is instructed to drop out, then the sequence thereafter will have an entirely different set of codons, since they line up differently. The fact that instead of yielding garbage the new series of codons codes for a useful protein is truly amazing! And apparently a few genes even code for 3 proteins!
Just how amazing this is can better be appreciated through an analogy. Let's imagine encoding some familiar fairytales in DNA. For our start codon, we can choose ATG (which does that in real DNA) and have it encode the phrase, "Once upon a time." Let's choose TGA (an end codon) to encode the phrase “And they lived happily ever after." With our other 62 codons, we can easily encode the English alphabet, along with punctuation marks, spaces, etc. With this system, then, we could encode the story of Snow White in DNA format. It would be quite a long "gene" in our Brothers' Grimm "genome," but still infinitesimally small. ("The information necessary to specify the design of all the species of organisms which have ever existed on the planet, a number estimated to be approximately one thousand million, could be held in a teaspoon and there would still be room left for all the information in every book ever written." Biologist Michael Denton)
Now imagine that we are such elegant programmers that we can take that same chain and splice out a few of the nucleotides so that the codons triplets are shifted over to line up in a completely different set of codons. And imagine now that the story has turned into that of Cinderella! (Now imagine that you have things programmed so that you can splice out a few different nucleotides and have the new coded information come out as Sleeping Beauty!)
Admittedly, the hypothetical codon sequences needed to program Snow White would be a whole lot longer than the sequence needed to program a typical protein just a few hundred amino acids long. Likewise, in real DNA coding, it is more than just the "Once upon a time" beginning that is the same, as the passed-over nucleotides are not at the very beginning. Thus, perhaps it's more like the story of Snow White being modified to where the seven dwarfs pull the pumpkin carriage to take her away at the stroke of midnight and the rest of the story line follows that of Cinderella. Anyway, while the analogy does push things a bit, it isn't far off the mark. We will leave to our readers' own imaginations the philosophical implications of this amazing fact, but no matter where you come down there, this is truly mind-boggling — even more so in my opinion than things on the other end of the scale of size: those hundred billion or more galaxies spread out through the universe!
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