Loss of gene function through rapid mitotic cycles in the Drosophila embryo

Analysis of rapid mitotic cycles in the Drosophila embryo show that these cycles constrain genetically-determined development during short 'phenocritical' periods by curtailing the length of genetic transcripts. The analysis concerned two Drosophila genes, knirps gene and knirps-related gene, which help determine abdomen segmentation. The necessary coordination of mitotic cycle duration and gene size probably works against rapid evolutionary change.