Correct option is B
Correct Answer: (b)
Explanation: Mutant forms of the ALS (acetolactate synthase) gene confer resistance to imidazolinone and sulfonylurea herbicides and are widely used as selectable markers in plant genetic transformation. These herbicides inhibit ALS enzyme activity in normal plants, but mutant ALS allows transformed plants to survive. Hence, the pairing of mutant ALS with imidazolinone resistance is correct.
Information Booster
· Selectable marker genes help identify successfully transformed plant cells.
· ALS encodes acetolactate synthase, a key enzyme in branched-chain amino acid biosynthesis.
· Imidazolinones are herbicides that target the ALS enzyme.
· Mutant ALS genes allow plant growth in the presence of these herbicides.
· Herbicide-resistance markers are preferred alternatives to antibiotic resistance markers.
Additional Knowledge
The nptII gene confers resistance to kanamycin and neomycin, not streptomycin. The aadA gene provides resistance to streptomycin and spectinomycin rather than rifampicin. The pat gene encodes phosphinothricin acetyltransferase, conferring resistance to glufosinate (phosphinothricin) and not penicillin. Therefore, only mutant ALS correctly matches with imidazolinone resistance.
