Making a pattern from no pattern
Fig 1. In 1952, Alan Turing presented a theoretical framework for biological pattern formation that explained how positional information can be generated in an embryo. At the beginning of the 21st century, the “Turing model” has become widely accepted throughout the scientific community.
Until 1952, when a period of little scientific progress in the field came to an end through the work of a single man, brilliant mathematician and theoretical biologist: Alan Turing. During that year, his now legendary paper, entitled “The Chemical Basis of Morphogenesis” offered a theoretical framework for biological pattern formation, thereby obviating any further need for speculation. By developing a mathematical model, Turing demonstrated that a combination of chemical reaction and diffusion - two diffusible substances interacting with each other - can generate a wide variety of spatial motifs, such as stripes, spots and spirals. He proposed that such reaction-diffusion mechanism can serve as the basis of pattern formation during morphogenesis. In mid 20th century, such a hypothesis was nothing short of amazing - and indeed, for many years to come, only few would grasp the scope of Turing's concepts - as it offered a biochemical basis for generating positional information without the existence of any pre-pattern. Or in other words, it described how non-uniformity can arise biochemically out of a homogeneous, uniform state - the scientific enigma that kept developmental biologist awake at night, in those days.