Class 12 NEET Biology Biotechnology and Its Applications

(a) : Transgenic plants are those plants in which a foreign gene has been introduced and stably integrated into host DNA. The first transgenic plants were produced in tobacco (Nicotiana tabacum). A gene resistant to PPT (L-phosphinothricin), an active ingredient of herbicide 'Basta', was isolated from Medicago sativa. It inhibits the enzyme GS (glutamine synthase) which is involved in ammonia assimilation. This gene resistant to PPT was incorporated into tobacco, as a result of which transgenic tobacco was produced which was resistant to PRT.