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The Flexibility of the DNA structure

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The Flexibility of the DNA structure

Postby Purplez » Sun Nov 05, 2006 12:52 am

I recently did a lab involving DNA extraction from Liver and Onions. One of the lab questions asks:

1. If DNA is a rigid structure, why do the DNA strands appear flexible? What features of DNA structure account for its stiffness? If DNA is rigid, how does it coil into tight spaces?

I just need a hint please!

Oh and why does DNA cling to glass? o.0

Thank you!
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Postby druid » Sun Nov 05, 2006 2:26 am

1. I think because of Length/Thinkness ratio. Alberts et al (MBoC4,p382) says us it's 90 degrees of bending per 200 nt. Also, it says that this ratio can be influenced by nucleotide sequence. Here you can find how DNA structure depends on its sequence content:
http://www.jbc.org/cgi/reprint/263/30/15535.pdf

2. If it's about stability then many bp interactions. Each of them is weak but they work together.

3. DNA accomodates into tight spaces by many levels of packaging with histones (or equvalent proteins in bacteria/virus though them have much less DNA amount compared with eukaryotes).
For example, 10nm fiber provides package ratio of ~6, 30nm fiber of ~40 and it's estimated that higher levels of compressing reach ~10000 ratio (Genes8, Lewin)
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Postby Purplez » Sun Nov 05, 2006 2:44 am

Awesome, thank you very much...I'll try to work out the answer from what you gave.
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Postby druid » Sun Nov 05, 2006 2:49 am

Always recheck data! ;)
I'm just a poor undergraduate student like you...
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