Researchers observed zygotal gene expression patterns during the first cell division.

Under the microscope, the two mating yeast cells fused zygotically, producing a diploid cell that divided to form a colony.

The zygote divides rapidly during the first hours after fertilization, setting the stage for embryonic development.

The biologist examined the zygotes under a microscope to monitor early development.

The researchers observed zygotic gene expression within hours after fertilization.