Question

A shuttle vector is defined as.
A. A plasmid capable of replicating in one organism
B. A plasmid capable of accepting only large DNA inserts
C. A plasmid incapable of replicating in cells
D. A plasmid capable of replicating in two different organisms

Answer 1

Vectors are DNA molecules that carry alien DNA and replicate within the host organism. Shuttle vectors can be used for prokaryotes as well as eukaryotes. Plasmid and bacteriophage are commonly used vectors, their number can vary within the cell.

Complete answer: Vectors are the DNA molecules that carry a foreign DNA segment and replicate within the host cell such as bacteriophages, cosmids, phagemid, BAC (bacterial artificial chromosomes), YAC (yeast artificial chromosome) animal and plant vectors, and shuttle vectors.
Plasmid DNA acts as a vector to transfer a piece of alien DNA attached to it.
Recombinant DNA = vector + insert
Mosquito is an insect vector that transfers the malarial parasite into the human body, similarly, the plasmid is used to transfer alien DNA into the host organism.
Shuttle vectors are those vectors that can be used for more than one organism like used for both prokaryotes and eukaryotes.

Vector	Maximum size of DNA insert for cloning
Plasmid	15kb
Phagemid	25kb
Cosmid	45kb
BAC	300kb
YAC	1400kb

So, our correct option is D. a plasmid capable of replicating in two different organisms.

Note: Plasmid and bacteriophage vectors are commonly used and have the capability to replicate within bacterial cells independent of chromosomal DNA. Bacteriophages because of their high number per cell, have high copy numbers of their genome within the bacterial cells. Some plasmid may have one or two copies per cell whereas others may have 15-100 copies per cell. Their numbers can even go higher.
The transfer of genetic material from one bacterium to another through the virus is called transduction.