1. –Relationship between the chiasma patterns and MI configurations of bivalent pairing with a distal FISH marker.
–Relationship between the chiasma patterns and MI configurations of bivalent pairing with a distal FISH marker. Each line represents two sister chromatids. A and B represent the two arms of a chromosome, and arm B is marked with a noncentromeric FISH marker, which allows distinction of the two arms. X...X between homologous chromosome arms A and B in first column represents a chiasmate condition, i.e., one or more chiasmata. The combinations of the two arms with or without chiasmata can produce four types of disomic MI configurations, i.e., ring bivalent (both arms A and B are chiasmate), rod bivalent with signals at the extremes (A is chiasmate and B is achiasmate), rod bivalent with signals in the middle (A is achiasmate and B is chiasmate), and two univalents (both A and B are achiasmate). The centromeres of the bivalents in the third column are marked with arrows. The top and bottom represent the two opposite poles. In this study, a distal 5S rDNA on maize chromosome 2L and a median 18S-28S rDNA on maize chromosome 6 were used to allow the distinction among the four types of MI configurations of bivalent pairing of chromosomes 2 and 6, respectively. The frequencies of these various types of MI configurations were used to estimate the average chiasmate arm frequencies and map lengths for chromosomes 2 and 6 according to the methods outlined by Reyes-Valdés et al. (1996).
YuanFu Ji et al. Genetics 1999;151:
Copyright © 1999 by the Genetics Society of America