In a genetic engineering experiment, a bacterial culture is transformed with a plasmid vector containing an ampicillin resistance gene and a -galactosidase gene (which has a cloning site). The culture is then plated on an agar medium containing ampicillin and a chromogenic substrate. After incubation, three distinct outcomes are observed for the bacterial cells: (A) Cells that fail to grow and form colonies. (B) Cell

Step-by-step solution

The agar medium contains ampicillin, an antibiotic. Cells that fail to grow (A) lack the plasmid entirely, meaning they do not possess the ampicillin resistance gene. These are non-transformants. Cells that grow have successfully taken up the plasmid and are transformants. Among these, cells that form blue colonies (B) possess an intact -galactosidase gene, which produces an enzyme that cleaves the chromogenic substrate to give a blue colour. This indicates no foreign DNA was inserted into the gene, making them non