noun, plural: maternal-effect genes
By maternal-effect, it means that during development the embryo does not express the products from this gene; it inherits the products synthesized from the gene of the mother (and the synthesis occurs well before fertilization).
Maternal-effect genes are required for the normal development of the embryo. They produce transcription products that establish polarity. These genes also determine the basic body plan of the embryo. In Drosophila embryogenesis, examples of maternal genes are bicoid, nanos and caudal.