Friday, November 28, 2014

The genome is neither a blueprint or a map, it's more like a set of Ikea instructions.

1. Make lots of cells by mitosis.
2. Now there are a lot of cells. If you are a cell on the surface of the ball of cells, turn on gene 125. If you are inside the ball of cells, turn on gene 452.
etc etc
4,567. If you are a cell next to some other cells that are next to some other cells that have gene 452 turned on, turn off gene 452 and turn on gene 681.
etc etc.

In other words, there is no way to easily "decode" the primary DNA sequence of a genome and "guess" what the organism would look like. Genes get turned on and off, proteins and other biomolecules get made, they assemble together (or not) and physically modify each other by phosphorylation, glycosylation, etc (or not), and cells end up having certain shapes, which in turn cause organs to end up having certain shapes, which end up making the whole organism have a certain shape. Some of this is encoded in the basic laws of physical chemistry, which even for a single protein cannot easily be applied. So it's no surprise that we are still absolute infants in our understanding of genomes. I consider this to be a project of centuries at least, hardly years or decades. That doesn't mean we can't answer some reasonable questions, like are there specific genes which if mutated cause someone to have high cholesterol (yes), or get lung cancer with high probability (I don't know). But these are just the tip of the real genomic information iceberg.