Which of the following statements are NOT true?

A. Plasmids are circular pieces of double stranded DNA that exist separately from chromosomal DNA. B. Plasmids that can be propagated in cells of two or more different species are called expression vectors. C. Shuttle vectors cannot be used in prokaryotes. D. A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted for cloning purposes.

Correct answer. Plasmids that can be propagated in cells of two or more different species are called shuttle vectors. An expression vector is generally a plasmid that is used to introduce a specific gene into a target cell. A shuttle vector is a vector that can propagate in two different host species. Hence, inserted DNA can be tested or manipulated in two different cell types. It can be used in both eukaryotes as well as prokaryotes.