Concerning the Origin of the Polytene Chromosomes of Diptera

Abstract

From an analysis of the literature on dipteran polytene (salivary gland type) chromosomes the author suggests that they arise during development in larval tissues fated for histolysis by duplication (polyploidy) and somatic synapsis of chromonemata which uncoil but are prevented from separating by a pre-metaphase mitotic block. Berger''s multiple complexes are represented as an intermediate stage in this process. The radial polytene synapsis is considered as arguing against Darlington''s precocity theory.