Final answer:
Plasmids are small, circular DNA molecules that replicate autonomously in prokaryotic cells. They can carry advantageous traits and be transferred independently of the bacterial chromosome.
Step-by-step explanation:
Small, circular DNA molecules that replicate autonomously in many prokaryotic cells are called plasmids. Plasmids are short circular double-stranded DNA molecules that can be transferred independently of the bacterial chromosome during cell division. They often carry traits such as antibiotic resistance and can be exchanged between bacteria.