Final answer:
Prokaryotes have a single circular double-stranded chromosome, one copy per cell. Genetic exchange between molecules of DNA can occur through the exchange of plasmids.
Step-by-step explanation:
In prokaryotes, the genome is composed of a single circular double-stranded DNA molecule. This genetic material is contained in a region called the nucleoid. Prokaryotes can also have smaller loops of non-essential DNA called plasmids. Bacteria can exchange these plasmids with other bacteria, allowing for genetic exchange between molecules of DNA.