Supplementary Figure 1: Phase-contrast and fluorescence images of lampbrush W-chromosome spreads.

(a, f, k) Images of chicken Z–W lampbrush bivalents in phase contrast, oriented with the terminal giant lumpy (TGL) loops and the W chromosome at the top and the Z chromosome at the bottom. Scale bar, 10 µm. (b, g, l) FISH localization of BAC probes (red) on the same lampbrush chromosomes counterstained with DAPI (blue). (c-e, h-j, m-o) Magnification showing the DAPI-intense chromomeres of the W chromosome (c, h, m), the BAC hybridization signal (d, i, n), and the merged image (e, j, o). Chomomere 1 is furthest from the chiasma, and chromomere 7 is adjacent to the chiasma. CH261-75N4 localizes to chromomere 2 (b, e), CH261-107E4 localizes to chromomere 4 (g, j), and CH261-114G22 localizes to chromomere 7 (l, o).