Mosaic pattern of X-chromosomal transcription in a strain of Drosophila melanogaster with aneuploid X chromosome.
Organisation and template activity pattern of salivary gland chromosomes of a segmental male aneuploid of D. melanogaster, carrying duplication for the segment 8C-20F of X chromosome, have been examined by in situ transcription. In an earlier study [Chatterjee, Chromosoma 91 (1985) 259], it was suggested that in male aneuploids, up to an additional length of 8C-20F, the template activity of X chromosome tends to remain at a male level and beyond that level shifts towards female level. A large scale search of the template activity pattern of the aneuploid carrying dp.(8C-20F) clearly indicates that presence of the duplication fragment to X in the normal karyotype (1X2A) lead to a varying degree of condensation of euchromatic regions of entire X chromosome (X + X fragment 8C-20F) starting from 'male' level, over a wide range of 'intermediate' level to a normal 'female' level. In this study, the individual cells of the aneuploid appeared to display their own state of X condensation and transcription. Although in the aneuploid, X chromosomal activity is not determined by a purely quantitative effect of X vs. autosomal material (X:A ratio = 0.81), the 8C-20F segment of X chromosome must contain some major elements concerned with the signal given by X:A ratio for X chromosome differentiation.
Chatterjee
R N
RN
Department of Zoology, University of Calcutta, India.
D000782:Aneuploidy; D000818:Animals; D004331:Drosophila melanogaster; D005260:Female; D008297:Male; D009030:Mosaicism / Q000235:genetics*; D014158:Transcription, Genetic; D014960:X Chromosome / Q000378:metabolism*