Question

12. A group of proteins control embryo development in Drosophila. Answer both parts of this question

A. What are Hox proteins and how do they work in the development of Drosophila embryos.

B. Describe the regulation of hox gene expression in embryo development of the Drosophila.

Answer 1

12.A
The Hox proteins are products of the Hox genes. These genes are a family of transcription factors, which are major regulators of embryonic development. The main function of these genes in drosophila embryonic development is in the segmentation of the embryonic body into the head, thorax and abdomen.

Briefly, the different families of Hox genes in the drosophila can be divided into the maternal effect genes, gap-genes, pair-rule genes and segment polarity genes. The maternal effect genes are produced by the mother and the mRNA’s are directly transmitted to the oocyte. The products of these genes are instrumental in setting up the anterior-posterior poles in the developing embryo. The proteins produced by the other families of genes are present in a concentration gradient across the length of the embryo. The concentration of each protein (termed as morphogen) decides the segmentation of the fly. These genes are active in the early stage of development, and they set up a broad blueprint for the development of the embryo. Once this is done, a regulatory cascade comes into effect, wherein the early stage proteins induce the production of late-stage proteins. These ultimately give definition to each of the segments and aid in further development of the body.

12.B
There are at the least three distinct regulatory patterns of control of the hox genes: transcriptional regulation signals which come from earlier segmentation genes; a system of cellular memory that is built upon the Polycomb (PcG)/trithorax (trxG) group proteins; and cross-regulatory interactions that are found among Hox genes themselves.