In the absence of antibiotic, there will be no pressure on recombinants to retain the plasmid (containing the gene of your interest). Since, maintaining a high copy number of plasmids is a metabolic burden to the microbial cells, it will thus, tend to lose the plasmid.

(i) The vector DNA is cut at a particular restriction site using a restriction enzyme ( to cut the desired DNA segment). Tha alien DNA is then linked with the plasmid DNA using an enzyme called ligase to form the recombinant vector.
(ii) Since a restriction enzyme recognizes and cuts the DNA at a particular sequence is called recognition site, the same restriction enzyme is used for cutting the DNA segment from both the vector and the other source.

1) Wrong fitting of electrodes.
2) Non - use of UV = radiations.
3) Inadvert contamination with nuclease
4) Wrong fitting of electrodes.

The experiment will not likely to be affected as recombinant DNA molecule is circular closed, with no free ends. Hence, it will not be a substrate for exonuclease enzyme which removes nucleotides from the free ends of DNA.

Formation of multiple copies of a particular gene is called gene cloning. A gene is separated and ligated to a vector like plasmid. The recombinant plasmid is introduced into a plasmid free bacterium through transformed bacterium through transformation. The transformed bacterium is made to multiply and form a colony. Each and every bacterium of the colony has a copy of the gene.