A “genetic roadmap” to track how an entire animal emerges from a single egg cell has been created by scientists at Harvard University.

Using genetic sequencing technology, they traced the fate of individual cells belonging to zebrafish and frogs as they divided and formed embryos over the first 24 hours of their existence.

The work showed how genes control the formation of complex, multicellular organisms from humble, single-celled origins.

The process, which they filmed, show the first division of the egg cell through to the formation of a ball of cells that will go on to become a zebrafish.

"Understanding how an organism is made requires knowing which genes are turned on or off as cells make fate decisions, not just the static sequence of a genome," said Professor Sean Megason, one of the co-authors of the study documenting this work.

"This is the first technological approach that has allowed us to systematically and quantitatively address this question."