Nucleic acid content in relation to cell size in the mature larval salivary gland of Drosophila melanogaster

Abstract

1. 1. The content of desoxypentose (DNA) and pentose (PNA) nucleic acids was determined in mature larval salivary glands of Drosophila melanogaster. Use of a stock giving giant and normal-sized larvae permitted the quantities (expressed on a per cell basis) to be related to different cell sizes. 2. 2. A micromodification of the Schneider method was developed which allows determination of samples consisting of 18 pairs of salivary glands (approximately 5400 cells) containing a total of 10–20 μg. N, 1–2 μg. DNA, and 10–20 μg. PNA. Data from some experiments using perchloric acid as the extraction medium are also included. Details of the extraction procedure and comparison of the nucleic acid values obtained from sugar determinations, phosphorus, and ultraviolet absorption are given. A discussion of the validity of the measurements is also included. 3. 3. The results obtained show that there is an increase of PNA per cell with doubling of cell size but no measurable increase of DNA. The increase in the PNA content is, however, not as great as that previously (1) found for nitrogen and alanylglycine peptidase in comparable material. 4. 4. The absolute values of DNA (284 μμg.) and PNA (2250–3600 μμg.) found per cell are compared with those found by others in related types and sizes of cells. In addition, the changes in DNA and PNA with cell size are correlated with similar measurements made elsewhere on materials undergoing various types of growth.