When we talk of transformation,we are talking of a biological method of the alteration of gene in a living cell especially as seen in a bacterial cells.
As a result of the incoperation and uptake of foreign genetic material from it's surrounding, the said bacteria then takes up the exogenous DNA,this it does by binding it with specific receptors that are present in its cells membrane or it can do so through diffusion.
However,the foreign DNA will either get incorporated in the DNA of the host chromosome or it will act like a plasmid and them express itself in the cell of the new host.
Then in conjugation,we see the transfer of circular plasmid DNA,this is transferred from one bacterium to another and it is done through cell to cell contact.
Also, transduction is still another way of transferring genetic materials,here the DNA is transferred to another bacteria via bacteriophage through lysogeny.
Now,in a given experiment,to identify if the reaction is transformation and not configuration and transduction,a controls sample will be provided,this control sample will contain DNase coupled with the reaction mixture,if there is a revelation of an exogenous DNA by the test sample,and there is no expression by the control,then we know that is transformation,we know it is transformation because DNase cleave free DNA and it will not be able to cut the DNA that is present inside the cell of donor bacteria that is in conjugation or bacteriophage(transduction).
Therefore,the addition of DNase in control sample can determine if the transfer of genetic materials in the test samples is transformation and not transduction or conjugation.