Figure 3: Relative sizes of IGCs in embryos, distinguished by the age. Results are presented as mean ± SEM with the level of significance . Digital images of embryo nuclei stained by antibody against SC35, a marker of speckles/IGCs, were used to measure the size of speckles. The average size of speckles at the stage of early zygote (20 h) was taken as a unit. The intensity of the column color conventionally reflects differences in transcriptional activity of embryo nuclei. The values of the relative size of speckles after the beginning of ZGA differ significantly from the stage of early zygote (20 h) at all stages studied (28 h, 32 h, 46 h, and 55 h), as indicated by asterisks. Not less than 15 embryos were analyzed for each age group; that is, more than 200 speckles were measured for each stage studied.