In bacteria, what is a small circular piece of DNA independent from the chromosome called?

• A. Plasmid
• B. Chromosome
• C. Genome
• D. Nucleoid

Answer: (A)

A plasmid is a small circular DNA molecule that exists independently of the bacterial chromosome. It replicates on its own and often carries genes that provide advantages, such as antibiotic resistance or the ability to metabolize certain substrates. The bacterial chromosome is the main circular DNA containing essential genes, not a separate molecule. The genome refers to the organism’s entire genetic content, which includes the chromosome plus any plasmids, not a single extra circle. The nucleoid is the region inside the cell where the chromosome resides, not a separate DNA piece. So the small circular DNA independent from the chromosome is a plasmid.