[ed. Pretty extensive overview, be sure to continue scrolling for the entire article.]
Back in 2001, the Human Genome Project gave us a nigh-complete readout of our DNA. Somehow, those As, Gs, Cs, and Ts contained the full instructions for making one of us, but they were hardly a simple blueprint or recipe book. The genome was there, but we had little idea about how it was used, controlled or organised, much less how it led to a living, breathing human.
Back in 2001, the Human Genome Project gave us a nigh-complete readout of our DNA. Somehow, those As, Gs, Cs, and Ts contained the full instructions for making one of us, but they were hardly a simple blueprint or recipe book. The genome was there, but we had little idea about how it was used, controlled or organised, much less how it led to a living, breathing human.
That gap has just got a little smaller. A massive international project called ENCODE – the Encyclopedia Of DNA Elements – has moved us from “Here’s the genome” towards “Here’s what the genome does”. Over the last 10 years, an international team of 442 scientists have assailed 147 different types of cells with 24 types of experiments. Their goal: catalogue every letter (nucleotide) within the genome that does something. The results are published today in 30 papers across three different journals, and more.
For years, we’ve known that only 1.5 percent of the genome actually contains instructions for making proteins, the molecular workhorses of our cells. But ENCODE has shown that the rest of the genome – the non-coding majority – is still rife with “functional elements”. That is, it’s doing something.
It contains docking sites where proteins can stick and switch genes on or off. Or it is read and ‘transcribed’ into molecules of RNA. Or it controls whether nearby genes are transcribed (promoters; more than 70,000 of these). Or it influences the activity of other genes, sometimes across great distances (enhancers; more than 400,000 of these). Or it affects how DNA is folded and packaged. Something. (...)
Think of the human genome as a city. The basic layout, tallest buildings and most famous sights are visible from a distance. That’s where we got to in 2001. Now, we’ve zoomed in. We can see the players that make the city tick: the cleaners and security guards who maintain the buildings, the sewers and power lines connecting distant parts, the police and politicians who oversee the rest. That’s where we are now: a comprehensive 3-D portrait of a dynamic, changing entity, rather than a static, 2-D map.
And just as London is not New York, different types of cells rely on different DNA elements. For example, of the roughly 3 million locations where proteins stick to DNA, just 3,700 are commonly used in every cell examined. Liver cells, skin cells, neurons, embryonic stem cells… all of them use different suites of switches to control their lives. Again, we knew this would be so. Again, it’s the scale and the comprehensiveness that matter.
by Ed Yong, Discover | Read more:
