Ans. D. All of the aboveExplanationPlasmidThey are extrachromosomal ds circular DNA molecules that exist in free state in the cytoplasm of bacteria, and also found in some yeasts.Plasmids are not essential for life.They can be present singly or in multiple numbers up to 40 plasmids per cell.They are capable of independent replication.Episome: Plasmids integrating with chromosomal DNA of bacteria.Curing: The process of eliminating the plasmids from bacteria. It can be spontaneous or induced by acridine, radiations, thymine starvations, growth at higher temperature.Classification of plasmids:On ability to perform conjugationConjugative plasmidsNon-conjugative plasmids.On compatibility between plasmidsCompatible plasmidsIncompatible plasmidsOn functionFertility or F-plasmids: Help in bacterial conjugation by forming the conjugation tube.Resistance plasmids: They code for resistance genes to various antibiotics.Col plasmids: They code for bacteriocins.Virulence plasmids: They code for virulence factors and toxins.Metabolic plasmids.Plasmids are also vectors in genetic engineering.TransposonsAlso called as jumping genes or mobile genetic elements.Transposons or transposable elements are bacterial genes that are capable of intracellular transfer between chromosome to chromosome, plasmid to plasmid, and chromosome to plasmid or vice versa.Transposons were first discovered by Barbara McClintock during her maize studies in 1940s and she was awarded noble prize in 1983.TransductionTransmission of bacteriophages from one bacterium to another, a part of host DNA may accidentally get incorporated into bacteriophage and then gets transferred to recipient bacterium.Two types of life-cycle: (a) lytic or virulent cycle (b) lysogenic or temperate cycle.Transduction transfers bacterial genes coding for drug resistance, e.g. plasmid coded penicillin resistance in staphylococci.