Final answer:
A selection marker on a plasmid is a gene that allows for the identification of transformed bacteria by conferring antibiotic resistance. Transformed bacteria can survive on antibiotic-containing media, indicating successful uptake of the plasmid. Additional reporter systems may be used to differentiate between different types of plasmids within the transformed population.
Step-by-step explanation:
A selection marker on a plasmid is typically a gene that confers resistance to antibiotics and is used to identify bacteria that have successfully taken up the plasmid through the process of transformation. During this process, bacteria are exposed to a plasmid containing the selection marker. Afterward, these bacteria are grown on a medium containing the antibiotic. Only the bacteria that have incorporated the plasmid and express the antibiotic resistance gene will survive and grow on this selective medium.
For example, if the selection marker is for ampicillin resistance, only transformed bacteria with the plasmid that expresses this resistance will grow on a medium containing ampicillin. In the case of E. coli being transformed with a plasmid carrying the amp resistance gene, growth on medium with ampicillin indicates successful transformation. If a second selection system was used, such as a substrate that changes color when metabolized by a reporter enzyme like β-galactosidase, this could further distinguish between bacteria with recombinant plasmids and those with non-recombinant plasmids. Non-recombinant plasmid-containing bacteria would typically form colored colonies, while recombinant bacteria would form white colonies due to disruption of the β-galactosidase gene.