XIV.—Cytological Analysis of Formaldehyde Induced Chromosomal Changes in Drosophila melanogaster

Publisher Website
Google Scholar
Abstract
Structural changes induced in male auxocytes after formaldehyde feeding were analysed cytologically. In comparison with the effects of X-rays (on mature sperm) there is: (1) a high proportion of mosaics; (2) an excess of repeats and deficiencies; (3) a shortage of translocations, and (4) fewer breaks in the heterochromatic regions.The very high frequency of mosaics and the low ratio of inter- to intrachromosomal changes may be explained by the delayed opening of potential breaks which tend to open simultaneously in the same chromosome but at different times in different chromosomes. The high number of “isochromatid” breaks (repeats) points to some connection with the reduplication cycle.The shortage of “eu-heterochromatic” changes in which “heterochromatic” breaks in salivary gland analysis are scored, can be similarly explained by a difference in the time of opening of potential breaks in the two types of chromatin.Initial non random distribution of breaks as well as the conditions of rejoining in premeiotic cells may also play some role.