A Second Code Controls the DNA Code
More has been discovered about the histone or nucleosome code (see 02/17/2004), a second genetic code independent of the DNA genetic sequence that directs the formation of proteins. The New York Times (see also Science Daily) reported on work by scientists at Northwestern University who found that the wrapping of DNA around nucleosomes (made of proteins called histones with varying “tails” of atoms) follows a pattern that regulates how genes are expressed. These patterns determine where transcription factors bind to the DNA:
The pattern is a combination of sequences that makes it easier for the DNA to bend itself and wrap tightly around a nucleosome. But the pattern requires only some of the sequences to be present in each nucleosome binding site, so it is not obvious. The looseness of its requirements is presumably the reason it does not conflict with the genetic code, which also has a little bit of redundancy or wiggle room built into it.
The transcription factors are prevented from binding to the wrong genes when they are wrapped around parts of the nucleosome that make them inaccessible.
The news story by Nicholas Wade states that this code is highly conserved (i.e., unevolved) in all living organisms:
The nucleosome is made up of proteins known as histones, which are among the most highly conserved in evolution, meaning that they change very little from one species to another. A histone of peas and cows differs in just 2 of its 102 amino acid units. The conservation is usually attributed to the precise fit required between the histones and the DNA wound around them. But another reason, Dr. Segal suggested, could be that any change would interfere with the nucleosomes’ ability to find their assigned positions on the DNA.
Yet the phenomenon might just as well be interpreted as intelligent design instead of evolution. In fact, Wade uses the D word at the end of the article, when describing how this new code explains a mystery about DNA – why there is redundancy in the number of codons that code for a given amino acid: “Biologists have long speculated that the redundancy may have been designed so as to coexist with some other kind of code,” he said. “And this, Dr. [Eran] Segal [Weizmann Institute] said, could be the nucleosome code.” See also the 07/21/2006 article on design-oriented research done at Weizmann (Rehovot, Israel).
The work is done by specialists in “computational biology” – a field of study more appropriate for design thinking than for evolutionary speculating. If Darwinists started computing the probability of evolution (see online book), they would get discouraged real fast.