alt Hacker NewsWhen I was restudying biology a few years ago, it was making me a little crazy trying to understand the structural geometry that gives rise to the major and minor grooves of DNA. I looked through several of the standard textbooks and relevant papers. I certainly didn't find any good diagrams or animations.
So out of my own frustration, I drew this. It's a cross-section of a single base pair, as if you are looking straight down the double helix.
Aka, picture a double-strand of DNA as an earthworm. If one of the earthworms segments is a base-pair, and you cut the earthworm in half, and turn it 90 degrees, and look into the body of the worm, you'd see this cross-sectional perspective.
Apologies for overly detailed explanation; it's for non-bio and non-chem people. :)
https://www.instagram.com/p/CWSH5qslm27/
Anyway, I think the way base pairs bond forces this major and minor grove structure observed in B-DNA.
It's not really just base pairs forcing groove structure. The repulsion of the highly charged phosphates, the specific chemical nature of the dihedral bonds making up the backbone and sugar/base bond, the propensity of the sugar to pucker, the pi-pi stacking of adjacent pairs, salt concentration, and water hydration all contribute.
My graduate thesis was basically simulating RNA and DNA duplexes in boxes of water for long periods of time (if you can call 10 nanoseconds "long") and RNA could get stuck for very long periods of time in the "wrong" (IE, not what we see in reality) conformation, due to phosphate/ 2' sugar hydroxyl interactions.