Step 1: Understand the role of a selectable marker.
A selectable marker is a gene present in a cloning vector that allows scientists to identify and select cells that have successfully taken up the recombinant DNA. Common markers include antibiotic resistance genes such as ampicillin or tetracycline resistance.
Step 2: Consider the experiment without a selectable marker.
If a plasmid vector does not contain a selectable marker, there will be no way to distinguish between the transformed cells (cells that received the plasmid) and the non-transformed cells.
Step 3: Predict the experimental outcome.
During the experiment, both transformed and non-transformed cells would grow together. Since there is no marker to identify or select recombinant cells, it would be extremely difficult to isolate the cells that actually contain the desired recombinant plasmid.
Final Answer:
If a plasmid without a selectable marker is used as a vector, recombinant cells cannot be identified or selected from non-recombinant cells, making the cloning experiment ineffective.