In a previous post I discussed entanglements in polymer
melts. I thought I’d spend sometime discussing some “practical” matters in
which entanglements play a role. Today, lets focus on a very special kind of
polymer: DNA.
You have a lot of
DNA in your body. In fact, each cell in your body has over 2 meters of DNA
packed inside a small bag called the nucleus. The diameter of a typical nucleus
is less than 10 microns.
If that hasn’t knocked you off of your seat yet, let me put
it in perspective.
To freaking Pluto; which they say is not even a planet anymore!
I have trouble dealing with headphones in my pocket,
and the nucleus manages to pack and use
all of that DNA inside it. How the heck does it do that?
The answer turns out to have some parallels in everyday
life. How do you deal with a really long water hose or vacuum cleaner cable? You roll it around something! You organize it!
Thus, DNA is not packed randomly. It is organized in a very
sophisticated hierarchical manner. This allows the nucleus to sequester a lot
of material and information in a very small compartment. Here is a nice video that explains this organization (DNA - nucleosomes - chromatin).
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