D. pseudoobscura male karyotype and Y Chromosome size variation. (A) D. pseudoobscura male karyotype. Shown are Muller elements: Muller elements A and D form the X Chromosome in D. pseudoobscura. (B) Measurements of Y Chromosome arms (ratio of long arm compared with short; y-axis) from chromosome spreads for each Y-replacement line (x-axis). Colors indicate the Y Chromosomes chosen for further investigation: blue, YL; yellow, YM; green, YS; dark blue, lines not further characterized. Dots correspond to outlier data that fall outside of Q1–1.5 × IQR or Q3 + 1.5 × IQR. (C) Diploid genome size estimations (y-axis) of Y-replacement line males (x-axis) from flow cytometry. The rightmost sample in red is the diploid genome size of females from the reference genome strain (MV25), the strain that was used to generate Y-replacement lines though backcrossing. The numbers show the inferred genome size of three males that were used for more detailed downstream analysis (and referred to as YS, YM, and YL). (D) Heterochromatin estimates in three selected Y-replacement line males. Top shows staining thoracic cells with propidium iodide, and bottom shows staining whole-brain nuclei with DAPI. Leftmost red boxplot is the sequenced/backcross female for comparison.
