Nusslein-Volhard and Wieschaus worked out a hierarchy for the control of early A/P patterning in the Drosophila embryo. The five steps in this genetic regulatory hierarchy include gap genes, homeotic/selector genes, maternal effect genes, pair rule genes, and segment polarity/segmentation genes.


Required:

Put these five classes of genes in their order of action from earliest to latest. Briefly describe what each set of genes is doing in this regulatory hierarchy that patterns the A/P axis.