How Your Body Packs Two Meters of DNA Into a Six-Micron Cell Nucleus

By Susannah F. Locke Posted 10.08.2009 at 3:41 pm 5 Comments

Fractal Globule Nearby regions on a DNA chain are represented using similar colors. Leonid A. Mirny and Maxim Imakaev

I can't seem to manage to keep my iPod in my bag for a day without creating an awful tangle of headphones, but my body's cells can work with two meters of stringy DNA into a tiny nucleus without making a knot. The secret is a structure called a fractal globule, according to a research paper to be published tomorrow in the journal Science.

First, the researchers found that a cell's DNA is organized in two compartments: an "off" area and an "on" area. Genes that aren't being used are tightly packed into the globule that acts like a filing cabinet, storing lots of info for later use. Genes that are currently being used are all together in a second area, where enzymes can access their sequences. Genes snake back and forth between the compartments as they're turned on and off.

But how does that happen without everything becoming a tangled mess?

Enter the fractal globule. This paper presents the first time this highly organized structure of strands has ever been observed anywhere. It keeps genes that are near each other on a strand also near each other in the ball, so that any point can be pulled in and out without knotting. "It makes it easy to pull a location out, read it, and then crumble it back and push it back where you took it from," lead author Erez Lieberman-Aiden, of Harvard University, told Popsci.com.

Fractal Globule Represented in Origami: Part of human chromosome 14 is folded here to make a fractal curve similar to what happens in cells. Designed and folded by Jason Ku. Photo by Erik Demaine. Thanks to Brian Chan, Erik Demaine, Martin Demaine, and Erez Lieberman-Aiden.

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5 Comments

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MarcusM

10/08/09 at 11:13 pm

"It makes it easy to pull a location out, read it, and then crumble it back and push it back where you took it from,"

Excuse my ingnorance, but exactly how does all this pushing and pulling take place? What's the mechanism? How does a molecule, marvelous as it is, do all this moving around? How does it know what it's supposed to read? It's not at all clear how all this activity takes place. I wish the writer didn't assume that we had this incredible body of knowledge.

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darcon77

10/09/09 at 1:07 am

Agree.
I don't see the point of the article, since the little it conveyed we already knew... from daily life.

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geebob

10/09/09 at 10:55 am

if you want the scientific principles here explained to you in detail, first go out and get an advanced degree in mathematics, microbiology, genetics or biochemistry. Next, go get the scientific paper that goes into the boggling details that is beyond the layman.

It's just odd to complain that popsci doesn't go into depth when the reality is that popsci brings science to the laymen who are far more limited in their ability to comprehend all these things. So this article is limited but it in fact brings some substantial enlightenment to the table. They've got a mathematical model now for how DNA winds up. Just because we've always known that DNA winds up doesn't mean that we had a model for how it did this. Furthermore, the structure in which is winds involves locations for genese that are on and genes that are off. If any laymen thought this beforehand, they were lucky guessers.

Thank you popsci for this tidbit on our deepening knowledge of God's creation. Keep up the good work.

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FaithMan

10/11/09 at 4:52 pm

Thanks VERY much for this article.

One of my all time favorite IMAX movies attempted to convey the dynamics of the DNA molecule. This 11 minute 3D film was released in 1985 and entitled, "The Universe, We Are Born of Stars". One of it's principle creators, was Dr. Nelson Max of Lawrence Livermore Labs. He was personally responsible for the DNA sequence.

I would like to see someone of his stature try to illustrate the dynamics of this two compartment idea. It would be incredibly difficult, but a joy to behold.

DNA is an enormous mystery. To call it a molecule is like saying the Empire State Building is a "shed". It's an enormous understatement.

I hope to hear more on this concept in your future editions!

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julesruis

10/26/09 at 7:24 am

For more information about fractals, see:
www.fractal.org

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