Review the model for control of evenskipped stripe 2 positio

Review the model for control of even-skipped stripe 2 positioning. Describe how you would predict stripe 2 to be affected in the following cases: giant mutant embryos, Krüppel mutant embryos, embryos from bicoid mutant mothers, embryos from mothers with one normal and one mutant copy of the bicoid gene, embryos from mothers with 6 copies of the bicoid gene.

Solution

The even-skipped stripe 2 is controlled by the promoter sequences that contains a series of enhancers that control the expression of the different segmentation stripes in the drosophila embryo. When the even-skipped stripped 2 is of most importance in drosophila segmentation and was predicted that the enhancer for the same is most conserved, including the DNA sequences of the protein binding and the spacing between them. To test this the four species of Drosophila were compared and was found that there is a number of nucleotide substitution in the regulatory protein binding sites for the bicoid, hunchback, Kruppel, and giant along with a change in the size of the enhancer. It is further hypothesized that the stripe 2 enhancers are functionally robust and its evolution is governed by the mutations in the binding sites of the regulatory proteins along with the spacing between the binding sites. In the case of embryos from mothers with 6 copies of bicoid gene, the even-skipped stripe 2 will be present as the stripe 2 enhancer is activated by the bicoid gene along with the hunchback gene.

In the case of Giant mutant embryos, there are chances of the presence of even-skipped stripped 2 will be present as the giant protein act as a repressor and the concentration of the protein is low in this region. In the case of Kruppel mutants, the even-skipped stripped 2 will be present as the Kruppel protein acts as a transcriptional repressor and the concentration of the protein is low. In the case of bicoid mutant mothers, the even skipped stripped 2 will probably be not present as the Bicoid protein acts as a transcriptional activator. In the case of embryos with one normal and one mutant bicoid gene, there are 50% chances of presence of the even-skipped stripe 2 as the mutant will act as transcriptional activator while the normal gene will act as transcriptional repressor causing the presence of the stripes 2.