Prophetic visions sometimes occur in the oddest of places. In the 1958 version of The Fly, a hapless scientist emerges from a matter transporter with a fly’s head fused to his neck. What cruel imagination could contrive to replace the human head and brain with the crude sensory apparatus of an insect? What the film’s makers couldn’t have predicted were the advances in molecular genetics that were to sweep through biology in the 1980s, enabling scientists to investigate how the brain develops in the embryo. Nor could they have known how crucial the fruit fly would prove to be as a model for understanding the development of the vertebrate head as a whole.
Over the past decade or so molecular biologists have unravelled much of the genetic blueprint that gives the fruit fly its distinctive, highly segmented body. Researchers believe that at least 100 genes are needed to specify the fly’s body plan in the embryo and that about 10 per cent of these genes provide the basic blueprint for the fly’s head. Now the spotlight has turned to vertebrate embryos. Scientists are asking fundamental questions about the genetic and cellular mechanisms that control the development of the brains and heads of vertebrates. How do cells know where they are in the head? Which genes programme the neural tube – the fine tube of tissue from which our brains grow – to develop in the right way?
INSECTS AND LEECHES
Clues are coming thick and fast from studies of two phenomena at the hub of developmental biology: segmentation and a stretch of DNA called the homeobox. Broadly speaking, segmentation refers to…
