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Fig. 3. The dynamics of chromosomal movement in differentiated and undifferentiated cells in primary cultures of eye imaginal discs. (A) Location of lacO repeats (stars) at 1F on the X and 59E on the 2nd chromosomes. The bottom circle is a schematic of these markers in interphase nuclei; d is the measure recorded at each time point. (B) Representative images from larvae containing the two above described lacO repeats and expressing mRFP-LacI fusion protein under an ubiquitin promoter. The top panel shows undifferentiated nuclei present anterior to the morphogenetic furrow and the bottom panel shows differentiated cells from ommatidial clusters present posterior to the furrow. The background fluorescence of mRFP demarcates the nucleus. The two bright dots are the two loci tagged with lacO repeats bound with mRFP-LacI fusion protein expressed under an ubiquitin promoter. (C) Plot of the average of mean square change in distance <
d2> vs. the time interval (t). The distance between the center of masses of the two tagged loci was computed over time. For undifferentiated cells data was collected from 19 nuclei from 7 eye discs dissected from third instar larvae. In the case of differentiated cells, the data was obtained from 21 nuclei from 9 eye-discs. Error bars show ± 1 standard error of the mean. Comparison of the height of the graphs reveals that the two loci are confined to a smaller nuclear space in differentiated cells, suggesting that chromosomal movement is more constrained during differentiation.
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