DNA Replication in Cells with Polytene Chromosomes
To investigate whether the structural features of the chromosome may determine the size of the replication units the polytene chromosomes of Diptera offer exceptional experimental possibilities. A polytene chromosome consists of a large number of homologous chromatids located side by side and is characterized by a specific and constant band- interband structure (1). This band- interband pattern corresponds on the chromatid level to a pattern of repeated units consisting of a region of highly compacted chromatin ( the chromo-mere) followed ( or preceded) by a non-compact region ( the interchromomere). Up to 95% of the total DNA is located in the chromomere.
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