Question

Circular DNA occurs in
A. Bacteria only
B. Bacteria and Chloroplasts
C. All virus
D. Bacteria, Chloroplasts and Mitochondria

Answer 1

Hint: A bacterial DNA that forms a closed loop and has no ends is known as circular DNA. It forms a closed loop and contains the entire genome.

Complete answer:
The threadlike structure found in the nucleus of most cells is a chromosome. This carries genetic material in the form of a deoxyribonucleic acid linear chain. The chromosome describes circular DNA comprising the entire genome in prokaryotes, or cells without a nucleus. The mitochondria which is present in most plant and animal cells has DNA. The chloroplasts of plant cells also contain DNA.In mitochondria and chloroplasts, the DNA molecules present are small and circular, much like the DNA of a typical bacterium. In a single mitochondria or chloroplast, there are normally several copies of DNA. The small circular chromosome located within the mitochondria is mitochondrial DNA. Mitochondria are organelles located in cells that are the development sites of energy. The mitochondria are transferred from mother to offspring, and hence mitochondrial DNA. Bacterial chromosomes are normally spherical, to create a full circle, with the double helix looping back. Eukaryotic chromosomes are linear, with the two distant ends sealing up the double helix. In a special compartment called the nucleus of the cell, eukaryotic chromosomes are located. The genomes of bacterial cells are known as prokaryotes. They lack a nucleus and are typically DNA molecules that are circular.

Hence, the correct answer is option (D)

Note: Chromosomes are much more complex in structure in eukaryotes, or cells with a different nucleus. Mitochondrial DNA is critically important for many of the mitochondrial pathways that generate energy.