Zygotically transcribed genes in zebrafish can be labeled with 4-sUTP and isolated, Related to Figure 1. (A) Zebrafish embryos injected at the 1-cell stage with 1nl 50 mM 4-sUTP at 4dpf. (B) Total RNA from 4-sUTP microinjected embryos (+4-sUTP) and uninjected wildtype control embryos (-4-sUTP) were loaded in equal amounts. The panel shows the membrane after transfer of the RNA and detection of biotinylated 4-sUTP, incorporated into RNA, with streptavidin-alkaline phosphatase. A developmental time course from 64-cell stage to 1k-cell stage is shown (indicated on top). An air-bubble impaired the transfer for the 256-cell stage (C) Agarose gel showing RT-PCR products from RNA isolated from 8-9hpf zebrafish embryos injected with 4- sUTP (+ 4-sUTP) or wildtype control embryos (- 4-sUTP). The upper two lanes show PCR products from the input material (before purification). The lower two lanes show PCR products from isolated newly transcribed RNA (after purification). Sixteen different genes (indicated on top) were analyzed from both known maternal and zygotically transcribed genes. Five µl PCR product were loaded per lane.