DNA is a long molecule. For example, a typical bacterium, like E. coli,
has one DNA molecule with about 3,000 genes (A gene is a specific
sequence of DNA nucleotides that codes for a protein. We'll talk about
this later). If drawn out, this DNA molecule would be about 1
millimeter long. However, a typical E. coli is only 3 microns
long (3 one-thousandths of a millimeter).So to fit inside the cell, the
DNA is highly coiled and twisted into one circular chromosome.
