In amongst the first cells of an embryo, proteins are moving about, directing life to instructions written in the genes. One of the best places to watch development in action is a Drosophila [fruit fly] embryo, where the journey from fertilisation to hatched egg takes just 24 hours. Like human embryos, early flies call on proteins called transcription factors, molecular switches that zip into the nuclei of different cells (purple) turning sets of genes on or off to coordinate development. Researchers found that between two precise stages 1–1.5 hours old (left) and 2.5 hours old (right) a transcription factor called Dorsal (green) moves to lower side of the embryo, helping some cells (purple) change into different tissues. This tiny tide of proteins – a process called facilitated diffusion – could answer questions about how our own development works, especially as we have similar transcription factors in charge of our earliest days.
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