The DNA content of polytene nuclei in midgut and Malpighian tubule cells of adultDrosophila melanogaster.

The amounts of DNA in midgut and Malpighian tubule cells of adult maleDrosophila melanogaster have been determined by Feulgen-DNA cytophotometry. The DNA values fall into discrete classes reflecting different levels of polyteny. The maximum level is 64C in the midgut, 256C in Malpighian tubules, and the modal values are 32C and 128C respectively. The data provide no evidence for extensive underreplication of heterochromatin. It is suggested that the reduced amount of satellite DNA found in the tissues of young adult flies may be a consequence of the fact that cycles of DNA replication started in the pre-adult stages are not completed until some hours after eclosion.