A tiny C. elegans nematode worm starts life as a single fertilised egg cell, known as a zygote. This cell grows and divides, making specialised new cells that form all the structures of its wriggly little body from tip to tail. But before any of that happens, this single cell has to make an important decision: which way is up? This short video reveals that clusters of a protein called PAR-3 (highlighted in red) move around inside a worm zygote after fertilisation, flowing from one side to the other and kicking off a series of molecular reactions that tell the embryo which way is up and down, front and back or left and right. This process, known as symmetry breaking, means that when the zygote divides for the first time it will give rise to two different cells which then go on to make separate parts of the worm embryo.
This video and research features in the free exhibition Deconstructing Patterns at The Francis Crick Institute in London, open until December 2018
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