We miss something important when we just look at the genome as a string of nucleotides with scattered bits that will get translated into proteins — we miss the fact that the genome is a dynamically modified and expressed sequence, with patterns of activity in the living cell that are not readily discerned in a simple series of As, Ts, Gs, and Cs. What we can't see very well are gene regulatory networks (GRNs), the interlinked sets of genes that are regulated in a coordinated fashion in cells and tissues.
What this means is that if you look within a specific cell type at a specific gene, its state, whether off or on, will be correlated in a coherent way with a set of other genes. Look in a developing muscle cell, for instance, and you'll typically find a gene called MyoD is switched on, and also other genes, like Myf5 and myogenin. Look further, and you'll find others like C-jun and cyclin-dependent kinase 4, that also have their activity modulated in predictable ways. And when we start poking around experimentally, we discover that the relationships are often directly causal, with certain gene products binding to and modifying the expression of other genes.
Wednesday, August 05, 2009
Every once in a while, PZ Myers stops beating the drum and remembers he's a scientist: