Important features about the structure of DNA:

DNA is made up of many Nucleotides (also called bases)

Nucleotides are made up of:

One Phosphate group (provides DNA with its negative charge and is the acid part of deoxyribose nucleic acid).
One ribose sugar that is deoxy (minus an oxygen atom) at the 2' carbon position.
One either purine (A or G) or pyrimindine (T or C) base.

Covalent bonds form the links between nucleotides to form one strand of DNA between the 3' OH of the Ribose, and a phosphate group which is attached to the 5' OH of the next nucleotide. The sugar residues are found every 3.4 Angstroms (0.34 nm).

Two strands of nucleotides are intertwined, held together by hydrogen bonds between a purine and a pyrimindine, (A always binds with T and C always with G). The two strands run in opposite directions (5'-3' and 3'-5'). One full helical turn consists of 10 nucleotides, and the diameter of the helix is 20 Angstroms (2.0 nm).

Illustration of DNA:

Phosphate and sugars are in the backbone on the exterior of the DNA double helix

Courtesy of the Biology Project

Watson and Crick's original paper:

http://exploritorium.com/origins/coldspring/ideas/printit.html

DNA is found in the nucleus of almost every one of your cells. If you were to stretch out all the DNA in one of your cells it would be 6 feet long, so how does it fit into your nucleus???

BIOTECH Project Department of Molecular and Cellular Biology The University of Arizona Nadja Anderson, Ph.D. nadja@email.arizona.edu http://biotech.biology.arizona.edu