Mendelian Ratios Despite Nonrandom Fertilization?

Abstract

Many genes which influence the vigor of sporophytes also influence the growth rates of pollen tubes. Thus, there should be many examples of nonrandom fertilization, and deviations from Mendelian expectations should be common. Such deviations, however, are reported very rarely. Examples of nonrandom fertilization are rarely discovered, probably not because they are actually rare, but because they are surprisingly difficult to detect. For example, if a 90% certainty of detecting a 1% deviation from an expected frequency of 50% is desired, the sample must include at least 26,546 observations. Evidence points to the polygenic control of pollen tube growth rate. Thus, a single gene should generally have a fairly small effect. If this effect is on the order of a 1% change in pollen tube growth rate, few experimental studies will detect the nonrandomness induced by such a gene. In that case, no significant deviations from expectations will be recognized.