Question

how do you make sure you obtain vectors with the gene of interest and not just some random fragment of DNA that a restriction enzyme also cut out.(both the GOI and the random fragment have the same ends)

Answer 1

Vector must be relatively small molecule molecule for convenience of manipulation.They must be capable of prolific replication in a living cell,therby enabling the amplification of the inserted donar fragmet.Their are numerous cloning vector in current use,and the choice between them often depends on the size of the DNA segement that need to be cloned.

One way of detecting a specific cloned gene is by detecting its protein product expression in the bacterial cell.Therefore, in these case, its necessary to be able to express the gene in bacteria;that is to transcribe it and translate the mRNA into protein.Most cloning vector do not permit expression of cloned genes,but such expression is possible if special vectors are used.However, because bacteria cannot process intrrons,the cloned sequences must be stripped of introns.The cloned gene is inserted next to appropriate bacterial transcription and translation start signals.Some expression vector have been desined with restriction sites located just next to lac regulatory regio.These restriction sites permit foreign DNA to the spliced into the vector for expression under the control of the lac regulatory system