Dynamics of pattern formation

Abstract

Experiments were designed to test the validity ofTuring's suggested pattern-forming mechanisms, which are initially capable of giving rise to only five to seven uniform structures.

TheOregon-R (wild-type), mass-cultured strain ofDrosophila melanogaster was employed. Selection for the regular arrangement of microchaetac on the margin of the fourth abdominal sternite was practiced for twenty generations. In the “L” line, individuals with six uniformly spaced bristles were selected as parents of every generation. Due to the absence of nine bristles dividing the sternal margin uniformly, the progeny was raised in each generation in the “H” line from males and females with nine as equidistant bristles as possible. The whole experiment was performed at 25±0.50°C.

Selection was effective in increasing the frequency of six regular bristles in the L line. But no progress in the desired direction was obtained in the H line, although the proportion of sternites with nine irregular structures was found to increase. The experimental results supportTuring's diffusion-reaction scheme of pattern formation in morphogenesis.