Key points are not available for this paper at this time.
Kleikamp, and Roeland Voorrips for their contribu-tions to this project and Dr. L. Dellaert for providing the irradiation-induced mutants. They also thank Dr. P. von Wettstein-Knowles for critically reviewing the manuscript. Address reprint requests to Dr. Koorn-
Koornneef et al. (1989) studied this question.