Extra Characters to the Biological Code
|April 21, 2009||Posted by Patrick under Biology, Science|
Even if compressed I’ve always thought that the known informational content was not enough data. This makes sense because from an engineering point of view because there doesn’t seem to be enough data storage space in a few billion base pairs of nuclear DNA to specify all the detail in a mammal or similarly complex animal. It’s enough room to store a component library of the nuts and bolts required to build individual cells of different types but not the whole animal.
Obviously no one can argue against the assertion that we do not fully comprehend the biological code. Unlike with computer code we cannot simply determine at a glance which informational content defines what biological function. The title of geneticist Sermonti’s book is “Why a Fly is not a Horse”. In it he writes the only thing we know for certain about why a horse is a horse and not a fly is because its mother was a horse.
Thus, based on our current level of knowledge, any calculations that quantify biological informational content are going to be rough estimates. Personally, when measuring the functional sequence complexity of code encoding proteins I’ve long biased any calculations I do by rounding up to several extra informational bits. And this action seems justified by this recent news:
“Anyone who studied a little genetics in high school has heard of adenine, thymine, guanine and cytosine–the A, T, G and C that make up the DNA code. But those are not the whole story. The rise of epigenetics in the past decade has drawn attention to a fifth nucleotide, 5-methylcytosine (5-mC), that sometimes replaces cytosine in the famous DNA double helix to regulate which genes are expressed. And now there’s a sixth: 5-hydroxymethylcytosine.
In experiments to be published online April 16 by Science, researchers reveal an additional character in the mammalian DNA code, opening an entirely new front in epigenetic research.
The work, conducted in Nathaniel Heintz’s Laboratory of Molecular Biology at The Rockefeller University, suggests that a new layer of complexity exists between our basic genetic blueprints and the creatures that grow out of them. “This is another mechanism for regulation of gene expression and nuclear structure that no one has had any insight into,” says Heintz, who is also a Howard Hughes Medical Institute investigator. “The results are discrete and crystalline and clear; there is no uncertainty. I think this finding will electrify the field of epigenetics.”
Genes alone cannot explain the vast differences in complexity among worms, mice, monkeys and humans, all of which have roughly the same amount of genetic material. Scientists have found that these differences arise in part from the dynamic regulation of gene expression rather than the genes themselves. Epigenetics, a relatively young and very hot field in biology, is the study of nongenetic factors that manage this regulation.”