Figure 4
Fertility rate and chromosome segregation in various genotypes. Fertility rate was expressed as progeny number for 100 mothers (A). The genotypes were either wt, with or without achiasmate X (X/FM7), mut-rec (mei-2181, ord5/Df) or mutant for yem-alpha (yem1/Df3450, X/FM7; yem1/Df3450 and mei-2181/8; yem1/Df3450). Chromosome segregation (B, C, D). In (B), the cross on which we based the analysis shown in (C). The bar graph (C) represents the % of total progeny falling in the 6 classes scored as indicated in panel C. Histogram drawing was after data contained in Additional file 1, Table S3. In grey, progeny obtained from eggs that underwent normal segregation. In brown, progeny with X missegregation as observed in mut-rec mutants; sterile males are X0 (y+w). In green, y sterile progeny specifically recovered in yem1 background. Sterile males have no paternal markers (yw+). (D) To ask how paternal chromosomes are transmitted and why the progeny in green are sterile we performed a cross between mei-2181/8; yem1/Df3450 females and males marked on both the sex chromosomes and the autosomes. Paternal X (Xp) is y+w as above and the Y chromosome bears a translocated X-linked y+ locus (Yy+). Chromosomes II have Gla or CyO dominant markers. 96% of the y sterile progeny had no paternal markers. Therefore the class represented in green in panel C represents essentially parthenogenetic females and some Xm0 males. One Xm chromosome bears a specific set of recessive markers (cv v f), which allows inferring the type of segregation (Xm1, Xm2). * As no y cv v f /y cv v f progeny were recovered, we infer that the females developed from diploid eggs that were y/y cv v f. More explanations are provided in the text and also in Additional file 1, Table S3.