How the mechanism works

Print edition : October 10, 1998

THE Terminator patent is titled, "Control of Plant Gene Expression". As the title suggests, the technology creates transgenic plants in which the expression of certain traits is introduced either by the application of an external stimulus through hybridisation or by the direct introduction of an enzyme.

Transgenic plants are transformed into Terminators by introducing into their genome a series of functionally inter-related DNA (deoxyribonucleic acid) sequences or genes.

The first DNA sequence or Gene-1 produces a substance that kills the embryo. But this gene has to be activated by a promoter, which is kept away from it by an intervening sequence (consisting of a blocking sequence, a spacer and another blocking sequence).

The second DNA sequence, or Gene-2, has a promoter that produces an enzyme which cuts the intervening sequence in the first DNA sequence, connecting the promoter and Gene-1. But the promoter in Gene-2 is kept repressed by a promoter in the third DNA sequence, or Gene-3, which gets activated by tetracycline at a particular stage of plant growth.

At the time of seed germination, Gene-3 gets repressed and activates Gene-2, which gives out a protein (recombinase), which cuts the intervening sequence in Gene-1 and connects the promoter and the Gene, thereby aborting the embryo.

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