[G O D I V A]

What is the reason for DNA having a major and minor grove?


Since I'm majoring in biochemistry my professor wanted an answer from (1) a biological point of view and (2) from a chemistry point of view, but I cant think of any

[Wreath]

well, it's quite useful when enzymes supposed to do something with DNA are searching for the "starting sequence". in major groove, you can always recognize the base pairs without unwinding the double-helix. it's coded by order of the groups CH3, H-bond donor, H-bond acceptor and H, which is different for each combination of base pairs. (you obviously must know the 5´-> 3´ ordering either.) grooves are usefull to be recognized with lot of DNA - protein links structures, like helix-turn-helix pattern, or zinc fingers, which are bonding to the grooves.
hope it helps, my brain isn't working so much after waking up 

[aHerraez]

I'd say that the reason is chemical. The biological viewpoint is of (functional) consequences, mostly what Wreath has said.

The chemistry: stereochemistry, each part of the DNA molecule has a specific conformation, so that the two nucleotides in a base pair cannot confront each other symmetrically. (Hard to explain with words, better look at some molecular models)
As a consequence, one side of the base pair is wider than the other, has more exposed groups.

[ggs]

Hi ya all,

Biological way of view is a consequences of the chemical one:)

Like the aHerraez said pairing nucleotides cannot align in the same plane (there is a little skew) and remember that nucleotides are not simetrycial. It could be less sgnificant if the purines (or pirymidines) would form hydrogen bond with themselves (but they do not). Because of that there a little bit more space on one side of the pairing nucleotides than on the other one.
To see what we are talking about see this picture
http://www.biochem.arizona.edu/classes/bioc461/GRAPHICS/Chapter27/Slide6.JPG

and this animation:
http://www.johnkyrk.com/DNAanatomy.html

Klich

www.bio-ggs.blogspot.com