[DNA reduplication cycle during chromosome polytenization in the salivary gland cells of Chironomus thummi larvae. III. The determination of the duration of the DNA synthesis period].

The duration of DNA synthesis in the salivary gland cells of Chironomus thummi larvae of the IV instar was determined by means of autoradiography and cytophotometry. Cells of different levels of ploidy differ in the duration of their DNA synthesis period. The tS of 2(10)c and 2(11)c cells was equal to 17 and 22 hours, respectively.

[Nonhomogeneity of the distribution of the absorbing substance in cytophotometry].

Results of two-wavelengths cytophotometry may be used to calculate m--the quantity of light absorbing substance, and gamma--the degree of non-homogeneity of distribution of the substance on a preparation. Formula (1) is almost free from any distributional error. Optical density limits of applicability of formula (3) for gamma are shown on fig.

[Quantitative analysis of the DNA content in salivary gland chromosomes of Chrironomus thummi in the larval and prepupal stages].

Relative DNA content during the polytenization of the salivary gland nuclei of Chironomus thummi was measured by cytophotometric and cytofluorometric methods. To estimate polyteny degree, DNA content was calculated in hemocyte and spermatocyte nuclei. Chromosome polytenization is associated with the 10th-12th replication rounds.

Quantitative analysis of DNA content in the salivary gland chromosomes of Chironomus thummi at larval and prepupal stages.

Relative DNA content during the polytenization of the salivary gland nuclei of Chironomus thummi was measured by cytophotometric and cytofluorometric methods. To estimate the degree of polyteny, the DNA content was calculated in hemocyte and spermatocyte nuclei. Chromosome polytenization is associated with 10 to 12 replication rounds.