Final answer:
Plasmids are extra-chromosomal genetic elements found in bacteria that carry advantageous genes. The function of SMAR in plasmids is to provide selectable markers in order to identify transformants and maintain the plasmid in the bacterial population.
Step-by-step explanation:
Plasmids are extra-chromosomal genetic elements found in bacteria that carry genes coding for certain advantageous enzymes, such as antibiotic resistance. They can replicate independently and can be used as vectors for molecular cloning and the production of important reagents. The function of SMAR in plasmids is to provide selectable markers that allow the identification of transformants and maintain the plasmid in the bacterial population.