The morphology of polytene chromosomes can vary widely due to the differing degrees of synapsis of the DNA strands. Below, each strand within polytene chromosome will be conditionally designated as chromatid. Polytene chromosomes develop from the chromosomes of diploid nuclei by successive duplication of each chromosome element (chromatid). If homologous chromatid conjugation is maximal, classic polytene chromosomes, i.e. cylindrical cables with a distinct banding pattern, such as those described for Chironomus tentans or D. melanogaster, are formed