maternal effect genes are expresses during oogenesis by the mother (expressed prior to fertilization) and develop the anterior-posterior and dorsal ventral polarity of the egg. the anterior end of the egg becomes the head; posterior end becomes the tail. the dorsal side is on the top; the ventral side is in underneath. the products of maternal effect genes called maternal m rnas are produced by nurse cell and follice cells and deposited in the egg cells (oocytes). at the start of development process, m rna gradients are formed in oocytes along anterior-posterior and dorsal ventral axes.