Genetic Control and Regulation of Developmental Pathways

From fruit flies to fallout: Ed Lewis and his science

“…During the 1960s, Ed began to study genes that behave as positive or negative regulators of the bithorax complex-what we now call the transacting regulators (Lewis, 1968). He also started to address the spatial and temporal control of development by bithorax complex genes through his analyses of genetic mosaics (Lewis, 1963(Lewis, , 1964. Using mosaics, he was able to ask whether the bithorax complex genes confer the fate of cells autonomously or whether they encode diffusible substances, which, therefore, function non-cell-autonomously.…”

An analysis of the Notch locus in Drosophila melanogaster

“…The interpretation of these observations and others, including polarity effects, prompted Lewis (1967) to suggest that a favorable comparison could be drawn between the bithorax pseudoallelic series and the operon system known in bacteria. For instance, the polarization effects of specific alleles on other subloci and the total inactivation of the entire complex by a particular rearrangement (independent of position effect variegation) are certainly analogous to similar phenomena characteristic of alterations to an operon complex.…”

“…The concept of a "complex locus" (first described by Dunn; see Lewis, 1963) Lewis (1964), the terms "pseudoallelism" and "pseudoallelic series", when applied to the complex loci, now imply the functional complexity associated with a particular, chromo somal region. Respect for Lewis' suggestion will be shown when using these terms in the discussion which follows.…”

“…The "blthorax" pseudoallellc series, located on chromo some III, is comprised of five groups of phenotypically distinguishable mutants, both recessive lethal and recessive visible, which apparently effect different segments of the developing embryo (Lewis, 1963(Lewis, , 1964. The primary mode of mutation is the transformation of one segment (or organ) into a different, but embryologically similar one.…”

“…The primary mode of mutation is the transformation of one segment (or organ) into a different, but embryologically similar one. For example, Lewis (1964) has demonstrated, by the appropriate genetic construction of specific intra-locus combinations, that it is possible to transform the normally vestigal secondary wings (the halteres) into structures very similar, if not identical, in appearance to the normal primary wings, resulting, quite literally, in a fly possessing two pairs of wings.…”