The chromosome segregation defects observed in Wapl^Δ/Δ oocytes are a consequence of the increased chromosomal levels of Scc1-cohesin loaded onto chromatin long after DNA replication and meiotic recombination are completed. (A) Representative stills of live-cell imaging videos showing chromosome segregation in Wapl^fl/flScc1^fl/fl, Wapl^Δ/ΔScc1^Δ/Δ, and Wapl^Δ/Δ oocytes. DNA is shown in magenta. The time displayed indicates hours after GV breakdown. Scale is the same in all images; scale bar, 10 µm. (B) Quantification of chromosome segregation defects during meiosis I observed in live-cell imaging videos of Wapl^fl/flScc1^fl/fl, Wapl^Δ/ΔScc1^Δ/Δ, and Wapl^Δ/Δ oocytes. Two Wapl^fl/flScc1^fl/fl, five Wapl^fl/flScc1^fl/fl (Tg)Zp3-Cre, and two Wapl^fl/fl (Tg)Zp3-Cre females were analyzed. The total number of oocytes analyzed is indicated in the figure. The graph shows the percentage of oocytes for each chromosome-segregation phenotype (indicated in the legend). (C) Representative images of pro-metaphase I spreads of Wapl^fl/flSmc3^fl/fl and Wapl^Δ/ΔSmc3^Δ/Δ oocytes. Centromeres are shown in red, Smc3 in gray, and DNA in blue. Scale bar, 10 µm. (D) Quantification of Smc3 fluorescence intensities per bivalent in relation to CREST fluorescence intensity in Wapl^fl/flSmc3^fl/fl and Wapl^Δ/ΔSmc3^Δ/Δ oocytes. Two Wapl^fl/flSmc3^fl/fl and two Wapl^fl/flSmc3^fl/fl (Tg)Zp3-Cre littermate females were analyzed. The total number of Wapl^fl/flSmc3^fl/fl and Wapl^Δ/ΔSmc3^Δ/Δ oocytes analyzed is indicated in the figure. P value is <0.0001 (Welch’s t test). (E) Representative images of pro-metaphase I spreads of Wapl^fl/flScc1^fl/fl and Wapl^Δ/ΔScc1^Δ/Δ oocytes. Centromeres are shown in red, Smc3 and Rec8 in gray, and DNA in blue. Scale bar, 10 µm; inset scale bar, 5 µm. (F) Quantification of Smc3 and Rec8 fluorescence intensities per bivalent in relation to CREST fluorescence intensity in Wapl^fl/flScc1^fl/fl and Wapl^Δ/ΔScc1^Δ/Δ oocytes. One Wapl^fl/flScc1^fl/fl and one Wapl^fl/flScc1^fl/fl (Tg)Zp3-Cre littermate females were analyzed. The total number of Wapl^fl/flScc1^fl/fl and Wapl^Δ/ΔScc1^Δ/Δ oocytes analyzed is indicated in the figure. Fluorescence intensities are shown in a whisker plot graph as in Fig. 2 B). P values are <0.0001 (Welch’s t test).