Fig. 11. Simulation of the development of the homozygous EphA3 knockin map in mouse colliculus compared to normal. The 100 retinal cells were assigned equiprobably to one of two categories, distinguished by the colours green (EphA3⁺) and black (EphA3^-). The initial pattern of connectivity was random, and initially there were weak gradients of ephrinA and ephrinB over the colliculus. The maps shown are the projections from retina onto colliculus with the projections from the EphA3⁺ and the EphA3^- cells shown separately. (A) Control. EphA densities in EphA3⁺ cells and the EphA3^- cells are determined as for the wild-type case used in Fig. 2. A highly organised map (bottom left panel) develops from an initially disorganised state (middle left panel). (B) Homozygous EphA3 knockin (##/++). The EphA densities as shown in Fig. 2A were used. From the initially disorganised map, two separate ordered maps are formed (bottom row), with the green EphA3⁺ map more rostral than the black EphA3^- map. The red rectangle in the top left hand figure of A,B encloses the set of retinal cells that were used to make the one-dimensional connectivity plots shown in Fig. 4G-L.