They have evolved into the best length for their environment.
How are DNA fragments separated using gel electrophoresis? ... A solution ofDNA molecules is placed in a gel. Because each DNA molecule is negatively charged, it can be pulled through the gel by an electric field. Small DNAmolecules move more quickly through the gel than larger DNAmolecules.Nov 20, 2007
Guanine and adenine, structure-wise, are purines.
