Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Super Helix
Name: Finoe
Status: Student
Grade:  Other
Location: N/A
Country: Hong Kong
Date: November 2008


Question:
My textbook stated that the DNA helix if further coiled to produce a super helix. I would like to ask that what is a super helix



Replies:
Imagine that a piece of yarn is a DNA double helix. Look at the yarn closely -- see how there are smaller strands wrapped around each other? This is a little like a DNA double-helix. Now take the ends of the yarn and twist them (keep twisting!). After a few turns, the yard will start to coil up on itself. Keep twisting and the yard will keep turning on itself more. This is a supercoil.

Here's an electron micrograph (a special kind of imaging) of supercoiled DNA:

http://cmgm.stanford.edu/biochem201/Slides/DNA%20Topology/072%20Supercoiled% 20DNA%20jpeg.JPG

Hope this helps,
Burr


I take your book actually said " The DNA helix is further coiled to produce a super helix "

while I am not familiar with the term superhelix, I am familiar with the structure of DNA.

If you take a piece of string and twist it, the fibers within the string take on the form of a helix - (Some people call this an elongate spiral, although technically a spiral is a flat widening curve like a nautilus shell)

If you continue to twist the string WITHOUT TENSION it will curl on itself and form a loop with a double twist. That is a similar structure to the superhelix form of DNA. There are twists within the twists, within the twists. Try it with your telephone cord if you have a half hour to spare untangling it afterward.

Nor is this structure exclusive to DNA - many proteins are similarly twisted, and that is one of the reasons why many proteins are flexible molecules, and why they can be so easily damaged by heat. When you cook an egg, you cause the twisted helical molecules of the albumen - which are normally springy and elastic, to become tangled and knotted. I often have kids think of a tangled slinky spring - the coils getting caught on each other, until you get a rigid mess - analogous to a hard boiled egg.

Nigel Skelton
Tennant Creek High School
AUSTRALIA



Click here to return to the Molecular Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory