Question

The small, circular extrachromosomal DNA called plasmid is found in
A. Viruses
B. Bacteria
C. Fungi
D. Plant cells
E. Animal cells

Answer 1

Some Plasmids are used in bacteriophages (viruses that parasitize bacterial cells). A Plasmid is a small molecule of extrachromosomal DNA in a cell that is externally isolated from and can replicate chromosomal DNA separately. It is common in bacteria, however, to find plasmids in archaea and eucalyptus species, as small spherical, two-stranded DNA molecules.

Complete answer:

Virus is composed of one type of nucleic acid (either DNA or RNA) which is wrapped in a protective coat made up of protein called capsid.
Generally, Bacteria is composed of single, circular and double stranded DNA molecules which is known as a bacterial chromosome. But sometimes extrachromosomal genetic materials are present in the form of small, circular and closed DNA molecules called plasmids. Plasmids are naked.
Fungi is composed of membrane-bound nuclei with chromosomes that contain DNA with non -coding regions known as introns and coding regions known as exons.
Animal and plant cells contain DNA as genetic material and consist of extrachromosomal DNA.

So, the correct answer is option B. Bacteria

Additional information:
The size of the plasmid varies from 1 to over 200 kbps.
Plasmid can replicate independently. In order to perform replication independently, it must contain DNA that can act as the origin of replication.
The self -replicating unit in plasmid is known as replicon.
Plasmids produces antibiotically active proteins or colicins which inhibits the other strain of bacteria in their vicinity.
Some plasmids act as sex or fertility factors which helps in bacterial conjugation.

Note:
R factors are also plasmids. They carry genes for the resistance of one or more drugs.
Artificial plasmids are used as vectors in molecular cloning.
There are also diverse roles in plasmids. They may contain genes that improve an organism's survival, either by destroying other organisms or by toxin output to the host cell. Those plasmids make the replication process in bacteria simpler.
As plasmids are so small, they typically have just a few genes with a particular feature (as opposed to a large amount of noncoding DNA). In a cell with various roles, several plasmids may coexist.