To obtain female embryos, we mated +; SD72/CyO females to 19-3, yw, Rsp[s]-B[s]/Dp(2:y)CB25-4, y+, Rsp[s]B[s]; SPSD/CyO males (both kind gifts from Cynthia Staber) to obtain +/Dp(2:y) CB25-4, y+, Rsp[s]B[s]; SPSD/SD72 males, which we then mated to yw; attP2{ PCNA-EGFP} females (kind gift from Shelby Blythe). We performed 0- to 4-h timed lays and collected and fixed embry- os according to Blythe and Wieschaus (2015). We then hand- sorted embryos using a Zeiss Discovery.V8 microscope under GFP excitation using an X-CITE 120Q stereo light source. We pooled 200 (NC 11–14) to 400 (NC < 11) embryos and performed ChIP as in Blythe and Wieschaus (2015) using 3 μL of rabbit anti-CLAMP antibody per sample. We synthesized libraries using the NEBNext ChIP-seq kit (New England Biosystems) and se- quenced libraries on an Illumina HiSeq 2500 in 2×100-bp mode. We mapped CLAMP ChIP-seq reads to the custom histone locus genome (McKay et al. 2015), allowing only unique alignments by using Bowtie aligner (Langmead et al. 2009).