DNA Double Helix

Thursday, January 21, 2010

DNA is a normally double stranded macromolecule. Two polynucleotide chains, held together by weak thermodynamic forces, form a DNA molecule.

Features of the DNA Double Helix

* Two DNA strands form a helical spiral, winding around a helix axis in a right-handed spiral
* The two polynucleotide chains run in opposite directions
* The sugar-phosphate backbones of the two DNA strands wind around the helix axis like the railing of a sprial staircase
* The bases of the individual nucleotides are on the inside of the helix, stacked on top of each other like the steps of a spiral staircase.

DNA Helix Axis

The helix axis is most apparent from a view directly down the axis. The sugar-phosphate backbone is on the outside of the helix where the polar phosphate groups (red and yellow atoms) can interact with the polar environment. The nitrogen (blue atoms) containing bases are inside, stacking perpendicular to the helix axis.


Post a Comment