The most commonly cited examples of these genes are engrailed and gooseberry in Drosophila melanogaster.
[4] Segmentation polarity occurs during the release of morphogens, which functions to differentiate patterns within sections.
[5] In Drosophila, the engrailed gene is expressed only in cells within the posterior section of every segment.
Engrailed expression is generally restricted to cells in the posterior compartment but research suggests it may have other functions.
[9] Research into zygotes of Drosophila have indicated that several segment polarity genes are vital for segmentation involved in neuroblast formation and differentiation of cell into their neuroblast identity; thereby, developing the central nervous system.