PMC:1285065 / 20852-22789 JSONTXT

{"project":"2_test","denotations":[{"id":"16299588-15545646-86025626","span":{"begin":572,"end":573},"obj":"15545646"},{"id":"16299588-7523244-86025627","span":{"begin":701,"end":703},"obj":"7523244"},{"id":"T41462","span":{"begin":572,"end":573},"obj":"15545646"},{"id":"T78420","span":{"begin":701,"end":703},"obj":"7523244"}],"text":"Assessing Chromosome Pairing in X/X Oocytes Homozygous for the c(3)G Mutation\nWe were concerned that the associations of homologous chromosomes into regional domains within the nucleus might constrain both X chromosomes into a small enough nuclear region that we might fail to see unpaired lacO couplets even if they did occur. To confirm that high frequencies of failed pairing could be observed, if they indeed occurred, lacO pairing was analyzed in oocytes homozygous for the c(3)G mutation, which disrupts the pairing of euchromatic regions during zygotene/pachytene [1] (Figure 5). These experiments differ from those presented above only in that we used Orb staining to identify meiotic nuclei [23] rather than C(3)G itself. Examining oocytes homozygous for both a lacO insertion at 11A and for c(3)G revealed 15/33 nuclei with two unpaired foci. There were only three nuclei in which two distinct GFP foci were paired (for examples of unpaired foci in this genotype, see Figure 5). The distribution of distances between foci in oocytes with two GFP foci is shown in Figure 3C. By multiplying the frequency of unpaired foci by two or by computing the fraction of two foci nuclei that were unpaired (15/18), we can estimate that the lacO arrays were unpaired in 83%–91% of the oocytes examined. Thus, we can easily observe a failure in homolog pairing in X/X females that are homozygous for c(3)G.\nFigure 5 Unpaired lacO Sites in c(3)G Mutant Oocytes for Both X/X and FM7/X Oocytes\nCytoplasmic protein marker ORB was used to identify the 16-cell cysts. It is present from region 2a, where it is evenly distributed in the 16 cells. At region 2b and region 3, ORB concentrates in the pro-oocytes and the oocyte. The GFP foci (green) in merge images in conjunction with DNA (blue, DAPI staining) and ORB (red). Two optical sections are shown in wildtype, while six to seven optical sections are shown in c(3)G mutants. Bars = 1 μm.\n\nU"}