Food Safety - The Oxford Topic of Food, Politics, and Society - page 596

A considerable body of genomic DNA sequence data has now been accumulated that
demonstrates that conventional methods of breeding are likely to produce more changes
in the genome DNA than do transgene insertions (Batista et al., 2008; Ricroch, Berge, and
Kuntz 2011, Weber et al., 2012). It has been reported that mutagenesis can result in thou-
sands of genomic mutations per cell, including point mutations, inversions, duplications,
and deletions. During a single growing season, dozens of DNA transpositions can occur in
a single crop plant. Varieties of the same crop may have genes that are present or absent in
other members of the same species and the position of genes of the chromosomes of two
varieties may differ markedly. On at least two occasions, the evolution of novel proteins
has been observed in crop plants. These latter three observations can be explained by the
extensive spontaneous random excision, relocation, and insertion of chromosomal DNA
fragments in recombinational or transpositional events (Weber et al., 2012).
Critics of transgenic crops assert two reasons for special need for safety regulation.
They argue first that all transgenic crops are fundamentally different from crops pro-
duced by other methods of breeding and, second, that the insertion of DNA coupled
with the introduction of heterologous genes makes transgenic crop plants inherently
more risky. Critics are reluctant to approve of any plant that is the result of the applica-
tion of in vitro DNA methodology and focus their skepticism on transgenic crops as a
class . In contrast, science-based risk assessment points toward the conclusion that genes
move across species lines in nature, that genes have been transferred into new species
as a result of plant breeding, and that both nature and breeding produce mutations and
unintended effects in crop plants. Risk assessors coming from this understanding, there-
fore, focus on the individual new variety and ask if the newly introduced phenotype, or
any unintended changes, will do unacceptable harm to consumers or the environment.
Safety assessment then uses case-by-case evaluation and does not presume a priori that
transgenic crops are either safe or unsafe. The standard by which new varieties are evalu-
ated is comparative and seeks to ensure that there is a reasonable certainty that no harm
will result if the food is consumed in the customary manner. Safety assessment does not
conclude that new varieties are absolutely safe, since zero risk is impossible to establish.
The assessment seeks to determine if new varieties are as safe as, or are safer than, other
varieties of the same crop. This process is sometimes referred to as comparative safety
assessment .
Composition as a Window on Intended
and Unintended Effects: Substantial
Equivalence
The cornerstone of comparative safety assessment is a comparison of the composition
of a new variety with its parental variety as well as with other representative commonly
cultivated varieties of the crop (König et al., 2004). Composition studies can be used