A Pairing-Looping Model for Position-Effect Variegation in Drosophila

Abstract

L. J. Stadler's critical review, ``The Gene'' (Stadler, 1954), was published shortly after his death in 1954, when genes were defined abstractly by mutation, not molecularly by sequence, as they are today. In Stadler's time, position-effect variegation (PEV) represented a challenge to any simple view of the gene, because a PEV mutation could act to silence multiple linked genes, a feature commonly referred to as ``spreading''. One extreme view cited by Stadler was Goldschmidt's contention that PEV reveals that genes do not exist, at least not as discrete entities. Whereas such uncertainties concerning the existence and nature of the gene were soon cleared up during the molecular biology revolution, the problem of spreading seen with PEV remains: how can a single lesion affect multiple discrete genes in a region?