Questions & Answers

Plasmid is a
(a)Single-stranded DNA
(b)Double-stranded circular DNA
(c)Extrachromosomal linear DNA

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Hint It is a piece of DNA that is different from the chromosomal DNA, which is all the genetic material found in an organism’s chromosomes. It replicates independently of chromosomal DNA. It is mainly found in bacteria, but it can also be found in archaea and multicellular organisms.

Complete answer
In bacteria, plasmids are present as small extrachromosomal double-stranded circular DNA. They are separated from chromosomal DNA and replicate individually. They are rarely found in archaea and eukaryotic organisms. They usually carry some genes like antibiotic resistance genes into the host organism. These genes provide an added advantage to the bacteria.

Additional information
Plasmids have many different functions. They may contain genes that improve the endurance of a life form, either killing different living beings or shielding the host cell by delivering poisons. Some plasmids facilitate the method of replication in bacteria. Since plasmids are so small, they typically only contain a couple of genes with a selected function (as against an outsized amount of noncoding DNA). Multiple plasmids can coexist within the same cell, each with different functions.

So the correct answer is ‘Double-stranded circular DNA’.

Note: People have created numerous utilizations for plasmids and have made programming to record the DNA successions of plasmids to be utilized in numerous different methods. Plasmids are utilized in gene-splicing to amplify or produce many copies of certain genes. In molecular cloning, a plasmid may be a sort of vector. A DNA sequence that helps in the transport of foreign genetic material is called a vector, it transports the genetic material from one cell to another while the genes can be further expressed and replicated. In cloning short segments of DNA, plasmids are very useful.