Question

Circular DNA molecule occurs in
A. Viruses
B. Bacteria only
C. Bacteria and Chloroplast only
D. Bacteria, Chloroplasts, and Mitochondria.

Answer 1

DNA stands for Deoxyribonucleic Acid which is a hereditary material and is transferred from one generation to the next generation. Circular DNA is that form of DNA that has no end and has closed loops.

Complete step by step answer: Bacteria are prokaryotic organisms that have single, circular DNA. The bacterial genome size varies from 130 kbp to 14 Mbp. The genetic material is found directly in the cytoplasm. The region where it is found is called the nucleoid. The bacterial DNA synthesized bacterial proteins by undergoing translation as well as transcription.
The chloroplasts or plasmids are semi-autonomous cell organelles as semi-autonomous cell organelles have their own DNA. Ct-DNA is that DNA that synthesizes the protein for its organelle. The Ct-DNA acts as a plasmid and it is used for manipulation of genes.

Mitochondria is also known as a semi-autonomous cell organelle that has its own DNA and can produce or synthesize its own protein. It also has a circular shaped DNA which is commonly called mt-DNA. This kind of DNA acts as a plasmid and is also used for the manipulation of genes.
Hence, the correct option is D-Bacteria, i.e., Chloroplasts, and Mitochondria.
Additional information:
-Plastid play several roles they are mentioned as below,
-They have contended a stellar role within the development of molecular biotechnology.
-They act as vehicles to introduce foreign DNA into the bacterium.
-The DNA they deliver contains genes that have antibiotic resistance.
-It is a therapeutic platform for treating infectious, genetic, and purchased diseases.

Note: The Chloroplasts and mitochondrial deoxyribonucleic acid are double-stranded whereas lower-class bacterium E. coli has single-stranded. Special forms of DNA (deoxyribonucleic acid) like cpDNA and mtDNA are provided to the deoxyribonucleic acid of chloroplasts and mitochondria.