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

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

Answer: (D)

In bacteria, genetic material exists mainly on a single circular chromosome, but there are also small circular DNA molecules that live outside of that main chromosome. These smaller circles are plasmids; they replicate independently and often carry extra genes that aren’t essential for basic life but can provide advantages, like antibiotic resistance. The nucleoid is simply the region inside the cell where the chromosome is located, not a separate DNA piece. The genome refers to the entire set of genetic material of the organism, not an individual DNA circle. So the small circular piece of DNA independent from the chromosome is a plasmid.