The DNA code, which translates DNA sequences into protein sequences, has always been claimed as extremely compelling evidence for evolution. The code was first described in the mid twentieth century and, among other things, was found to be universal, or nearly so. The same DNA code is used in the cells in your brain and your big toe. The same DNA code is used in different species. The same DNA code is even used across the major kingdoms. All tissues, all species use the same code? Surely they were not independently created—they must have evolved. And if the code varied, on the other hand, evolution would surely be falsified. In one fell swoop, the DNA code not only is another compelling evidence for evolution, it also demonstrates that evolution is falsifiable, a badge that is crucial for evolutionists who seek to distinguish themselves from those religious rascals. But now a new code has been discovered and, believe it or not, it is not universal.
Most people understand that genes are sections of DNA that code for molecular machines such as proteins. But what is less familiar is that in higher organisms many of the genes are broken up into expressed regions, or exons, which are separated by intervening regions, or introns. After the gene is copied the transcript is edited, splicing out the introns and glueing together the exons. Not only is it a fantastically complex process, it also adds tremendous versatility to how genes are used. A given gene may be spliced into alternate sets of exons, resulting in different protein machines. There are three genes, for example, that generate over 3,000 different spliced products to help control the neuron designs of the brain.
But how does the splicing machinery know where to cut and paste? The answer is that there is an elaborate code that exciting new research is helping to elucidate. The new massive study systematically analyzed how genes are alternatively spliced in four different types of mouse tissue: central nervous system tissue, muscle tissue, digestive system tissue, and whole embryos.
The study found significant signals that the splicing machinery seem to use to decide how to do its splicing. This splicing code is extremely complicated, using not only sequence patterns in the DNA transcript, but also the shape of transcript, as well as other factors.
What is also complex about the new code is that it varies substantially across the four tissue types. There is still much to learn, but there certainly is no question that this is no universal code. Is evolution still falsifiable?
