[DNA content, replication and transcription rate in different site of the X-chromosome of Drosophila melanogaster].

Duration of replication period and relative content of DNA and chromosomal newly-synthesized RNA were determined in nine sites of the region 1A1-3C8 in the polytene X-chromosome of D. melanogaster. Determination of DNA content by cytophotometry of Feulgen stained preparations and by autoradiography after long-term [3H]thymidine labeling gave similar results for all nine sites. The smallest portion of the chromosome in which DNA content could be measured by cytophotometry was about 2-10 bands. The mean DNA content per one band measured separately in 25 sites of the 1A1-3C8 region containing 109 bands differs in 8 times. Calculations show that different chromomeres of elementary chromosome (chromatide) contained from 8 to 65 X 10(3) bases pairs. No additional DNA replication was shown to be involved in the process of 2B region puffing. The duration of replication period was found to correlate negatively with the level of the transcription rate in nine sites of the 1A1-3C8 region of the X-chromosome (r = -0.65). The transcription rate correlates negatively with the DNA content in the largest band for each of nine sites. No significant correlation was obtained between duration of replication period and DNA content in the largest band for each of nine regions.