Plant polytene chromosomes

Polytene chromosomes are structures found in highlyspecialized tissues in some animal and plant species, whichare amplified through successive cycles of endoredupli-cation, finally producing several copies of each chromo-some. For this reason, they have been very important inelucidating chromosome fine structure and physiology,especially in diptera.In plants, polytene chromosomes have been observedin only a few species, and seemed to be restricted to ovaryand immature seed tissues, e.g., in