Structure of the Salivary Gland Chromosomes of Diptera

Abstract

On the interpretation presented here the giant chromosomes of dipteran larvae consist, like mitotic chromosomes, of a number of helically coiled chromonemata. The chromo-meres in the giant chromosomes are misinterpretations of coiled structures, as has been demonstrated for meiotic and mitotic chromosomes. It is shown here how the appearance of bands and interbands may be caused by complex coiling of a bundle of chromonemata. The chromonema itself is uniformly Feulgen-positive. The giant size of these chromosomes would then be due to: great increase in length of the chromonema (longitudinal growth of individual genes); increase in the number of chromonemata by endo-mitosis; and lateral separation of the coiled chromonemata.