There are several sources of data from which one can obtain the information needed to establish estimates of the likelihood that the adverse effects may materialise. One such example can be seen when assessing the probability that a novel gene from an LMO introgressing into other organisms in the environment.

1. In a case where undesired outcrossing of the transgene with a non-modified organism is determined to be possible (i.e. the two species are sexually compatible), the risk assessment may consider both the likelihood of the outcrossing and, if relevant, the likelihood of the LMO progeny to persist or proliferate. Considerations on the latter may be based, for example, on assessing whether or not the transgene would affect the fitness level of the progeny (i.e. the capability of individuals to compete and reproduce in a given environment). If the transgene induces a positive fitness effect, the likelihood that the population resulting from the outcrossing would increase is high. On the other hand, transgenes that have a negative fitness effect would result in a low likelihood that the resulting population would increase. Transgenes that have a neutral impact on fitness may persist in populations at low levels depending on the rate of outcrossing or introgression as well as the overall population dynamics of the species.