Watson and Crick Model of DNAThe following are the features of the DNA molecule as described by Watson and Crick in 1953.
Components of DNADNA is composed of two chains of repeating nucleotides. Each nucleotide consists of three components. These components are:
Types of DNAThe DNA molecule that Watson and Crick described was in the B form. It is now known that DNA can exist in several other forms. The primary difference between the forms is the direction that the helix spirals.
A, B, C = right-handed helix
B is the major form that is found in the cell. Z-DNA was initially found only under high salt conditions, but the cellular environment is actually a low-salt environment. The question then is whether type Z exist under cellular conditions. Several features have been discovered that can stablize Z-DNA under in a low salt environment.
In addition to the direction the molecule turns, several other differences exists between the various forms of DNA. The following table summarizes the features of the different forms of DNA.
Copyright © 1998. Phillip McClean