CYTOMORPHOMETRIC ANALYSIS OF DROSOPHILA-M ELANOGASTER MEIG - POLYTENECHROMOSOMES IN RELATION TO HETEROSIS, SELECTION FOR ADAPTIVELY VALUABLE TRAITS, AND SEX

Four classes of cell nuclei containing polytene chromosomes of differe nt diameters were detected in the salivary glands of Drosophila at the stage of 0-hour prepupae. The diameter of chromosomes was shown to de pend on the level of polyteny. In the selected highly inbred lines LA (low activity) and HA (high activity) and in their F1 hybrids LA x HA and HA x LA, the ratios of nuclei containing chromosomes with differen t levels of polyteny were analyzed. It was established that chromosome s of an inadaptive line LA have a decreased level of polyteny. The hyb rids were superior to both parent lines in terms of the trait studied. Giant chromosomes of line and hybrid females had higher levels of pol yteny than male chromosomes. It is shown that the level of polyteny of giant chromosomes in Drosophila lines and their hybrids is correlated with differences in traits with a high adaptive value, such as rate o f development, fertility, heat resistance, competitiveness, etc.