Distinguishing Left & Right-Handed DNA: A, B, & Z Types

[zmike]

Hi

How do I tell whether the DNA strand is left or right handed? (for some reason I keep getting right handed for all 3 types of DNA even though this shouldn't be right?)

and is there any difference between A,b,z DNA BEYond that there is a change in the spacing of bp before a twist?

thanks

 

[nobahar]

Hello!
The best way, I feel, is to look at the backbone (of sugar and phosphate) as it passes along the front of the molecule: if it is going up and to the right, it's right-handed; and if it is going up and to the left, it's left-handed.