At least in a specific experimental context and with specific animal models. When they mixed the embryos of a frog and an axolotl, there were no genes in their genome which could predict whether a "frogolotl" will have legs.
You do realize this is untrue?
But I remember he was mentioning some study in left/right asymmetry in DevBio, where they've shown that it's cell potentials/bioelectric signalling and not genes that determine the left/right asymmetry in embryos.
No, they've shown that electric signaling is how the genes determine the left/right asymmetry in embryos.
How do you think it is that the same thing happens so consistently every time a new organism develops? Where do you think the electric gradients come from?