In my biochemistry class, we learned that transcription factors regulate the transcription of genes. However, transcription factors are also coded by genes, so what activates the transcription of genes that code for the first transcription factors during development?
The first transcription factors for the first transcription after fertilization are already present in the ovum (egg) before it is fertilized.
Generally, all the machinery needed for transcription, translation, and the rest of the many necessary cellular functions are already present in a cell before it divides and develops. This chain of dependency goes back eons of time to the origin of cells and the very origin of life.