Control early embryo development.

Maternal effect genes are genes of the mother that code for cytoplasmic determinants, substances deposited by the mother in the eggs she produces that regulate the expression of genes affecting the early development of the embryo

The products of maternal effect genes determine the body axes of the offspring.

Experiments lead to the understandng of how these genes work. The principle that a gradient of molecules can determine polarity and position has proven to be a key developmental concept, that the concentration of the products of the genes signal the determination of axes.