How is transposition frequency determined?
The most commonly used measure of germinal transposition frequency is the percentage of F2 progeny with a transposed element (Schmidt and Willmitzer, 1989; Altmann et al., 1992; Honma et al., 1993; see Arabidopsis transposon tagging references). However, this is not a valid measure of germinal transposition frequency because transposition often occurs early enough in development to give multiple progeny carrying the same transposed element. • Problem: multiple siblings from a single transposition. We examined 2-6 sibling plants from 19 progenies for the location of the TrE by blot hybridization and found that only 2 progenies (11%) had a different element in one or more of the siblings examined. • Solutions: • Use a different estimate of transposition frequency: to avoid erroneous over-reporting, we use the fraction of F1 plants showing at least 1 germinally transmissible excision or transposition event as the measure of the germinal transposition frequency. Because transposition comme
