A fertilized egg or zygote occurs just after the gamete union happened, at that moment the ploidy of the organism is restored, genetically all the genes are on, this means all are active and at that moment it will start cellular multiplication, now each cellular layer will start to differentiate by turning off certain genes, and genes like Hoax genes will start to guide the body plains, meanwhile in an adult animal no just tigers we have that the full-body plane has been already developed and each cellular line has been differentiated, DNA in every cell is methylated as differentiation already occurred, so even when genetically speaking of DNA the sequence is the same in the zygote as the adult tigger the DNA methylation pattern is totally different, without considering the total biomass increase directed by gene expressions.