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. Author manuscript; available in PMC: 2023 Jan 29.
Published in final edited form as: Curr Top Dev Biol. 2021 Apr 19;145:167–204. doi: 10.1016/bs.ctdb.2021.03.003

Fig. 2.

Fig. 2

The embryonic timing of zygotic genome activation. Embryonic stages of Xenopus tropicalis development (Nieuwkoop & Faber, 1994) are superimposed on a graph of mRNA expression profiles of several genes. Time in hours post fertilization (hpf ) is presented on the X-axis. foxh1 mRNA is shown as an example of a maternally deposited message that increases its levels by cytoplasmic polyadenylation in the period before ZGA. nodal3.1 and sia2 are two examples of genes that begin their pre-MBT transcription between 3 and 3.5hpf, which corresponds to the period between 64 cell and stage 7. gsc, ventx and sox17 are examples of genes that begin transcription at MBT. Data and 95% confidence intervals are derived from Owens et al. (2016) and the Y-axis values use a square root scaling.