Transgenes must be characterized appropriately for an environmental risk assessment. They can be designed to minimize possible environmental risks. Full control of gene transformation is not possible at present. Multiple transformations, duplications, inversions and mixtures of native and transgene DNA may occur, possibly resulting in expression of unintended transgene products, altered expression of native plant genes, and plants with new and unexpected traits.

Characterization of a transgene requires examination of the structure of the transgene(s) as integrated in the plant (locus structure), and of the patterns of expression of the transgene product(s) as the plant develops.

Step 1. Transgene Locus Structure. Complete sequencing of the transgene and flanking regions is essential to characterize the following:
- number of transgene loci (locations in plant genome)
- number of copies of transgene product DNA at each locus
- occurrence and number of marker genes
- all potentially expressed transgene DNA (including open reading frames)
- site(s) of integration in the crop plant (insertional mutagenesis, ectopic expression)

Step 2. Transgene Expression. The molecular characterization of the transgene is necessary but not sufficient for characterizing expression. Estimation of transgene product concentration in various plant parts over the development of the crop is essential. Additionally, because transgenes are integrated into the plant, they could affect expression of other plant traits. Therefore it is also necessary to characterize their expression in whole plants growing in field environments.

Step 3. Transgene Transmission. Transmission of transgenes from one generation to the next should be stable. Does a different genetic background alter expression?

Environmental risk can be minimized by appropriate transgene design. As a first approximation, transgenes at only one locus, with one copy at the locus, no duplications or inversions, no marker genes, no new open reading frames and no alteration of native plant gene expression will require a simpler environmental risk assessment than other more complex transgenes.

Teaching tools are in development for this section.

A Southern Blot test. Column No. 2 shows a plant that contains transgene DNA at four locations or loci.

pink bollworm in boll

cotton flower