Gap genes stand at the top of the zygotic segmentation hierarchy in Drosophila. Their expression domains are set up by a combination of maternal regulatory signals and interactions among themselves. In addition, these regulatory pathways are partially redundantly specified by the maternal and zygotic genomes, or by multiple zygotic gene products. The gap genes code for transcription factors which exert their function by foming short‐range morphogenetic gradients; differential concentrations of these transcription factors can either act as activators or as repressors (...) for the expression domains of neighbouring genes. It is possible to view the gap genes as a system of genes that subdivides the embryo by forming an activation‐repression cascade proceeding from anterior towards posterior. (shrink)

There is increasing evidence for the wide‐spread existence of functionally redundant genetic pathways in developmental processes. However, both their significance and manner of evolution are still matters of debate. I will argue here that redundancy of gene actions may, in fact, be a necessary requirement for the development and evolution of complex life forms. One can view development as a process that transmits information from the egg to the adult organism. Transmission of information is, however, always an error‐prone process, which (...) can only be safeguarded by including redundancies in the message. Molecular examples for well analysed redundant processes indicate that redundancies may best be understood within a conceptual framework of overlaps between different gene functions. (shrink)

We discuss, within the framework provided by a recently developed variational method, transposition-invariant field equations for unified field theories. Systems that are, in addition, invariant under Weyl-type gauge transformations or lambda transformations are derived. It is found that in a weak field limit two of the systems contain the equations of general relativity and the covariant Maxwell equations for a charge-free region.