THE WAXY LOCUS IN MAIZE III. EFFECT OF STRUCTURAL HETEROZYGOSITY ON INTRAGENIC RECOMBINATION AND FLANKING MARKER ASSORTMENT

Abstract

ABSTRACT The effect of heterozygosity for structural rearrangements on recombination between two wx heteroalleles (C and 90) and the pattern of flanking markers in the resultant Wx gametes has been examined. The rearrangements are Tp9, an insertional translocation in which a segment of chromosome 3 has been inserted into the short arm of chromosome 9 close to the wx locus; In9a, a long pericentric inversion with wx in the inverted segment; and Rearr 9, a complex rearrangement of chromosome 9. Heterozygosity for rearrangements decreases the frequency of Wx gametes to varying degrees.—Heterozygosity for Tp9 enhances the proportion of Wx gametes that are apparent convertants and allows the conclusion that such gametes do not normally arise from an exchange in the wx locus plus a second exchange distal to wx. Heterozygosity for In9a markedly decreases the frequency of Wx gametes that are recombinant for outside markers but does not decrease the frequency of convertants.—Heterozygosity for Rearr 9 permits a low frequency of Wx gametes, all of which are apparent convertants.—A high proportion of the convertants have the flanking markers that entered the cross with C so recombination is polarized in normal homologs and in heterozygotes for all rearrangements.