Question

Write one paragraph describing the structures of normal phenotype of a wild type embryo like a different body regions, segments and denticles. Use these three figures when you describe.

Thank you

wg hh en ..1 234 5 6 NNNNNNNNN1 234 5 6 NN

Answer 1

The image represents a post-13 hour embryo of Drosophila melanogaster as the segments are formed which is evident in the top fig. Each segment is flanked by a band of denticles ( zoomed in fig is the lower left corner one). Denticles are formed by cells in that region by developing actin-based protrusions. These discrete segments are formed as a result of differential expression of specific proteins (transcription factors) which inturn result in the differential spatial expression of other downstream proteins. These transcription factors are kept under a common category called the pair-rule genes which regulate the expression of segment polarity genes. Engrailed (en) and gooseberry (gsb) are 2 segment polarity genes which are differently expressed in different parasegments (parts of a segment) under the influence of different pair-rule genes. These inturn active the wingless (wg) and hedgehog(hh) signalling (as shown in lower right corner) which dictates the anterior posterior axis in the segment.