It is difficult to assume that the massive number of co-ordinated developmental sequences in a developing embryo is controlled by molecular signalling alone. Is anyone aware of a molecular or developmental clock within the genome which control the on off states of the genes concerned with developmental sequences? If it has not been reported is it likely to exist? (This is not about the molecular clock in evolution.)
Assuming there is a molecular clock, is it possible that the clock is switched on at the time of fertilization, and the zygote transfers the elapsed time to the progressive generations of the cells?