Practice question

During early Drosophila development before cycle 14, zygotic genome remains largely quiescent with only minor early zygotic genes transcribed. Embryo relies entirely on maternal products loaded during oogenesis by nurse cells, including mRNAs for bicoid, nanos, dorsal, gurken, and histones supporting rapid mitoses. These maternal determinants drive syncytial divisions, nuclear migrations, axis establishment and positional information. Activation of gap genes, pair-rule genes and cellularization requires maternal gradient interpretation. Therefore early patterning, cleavage and axis specification before maternal-to-zygotic transition are governed by maternal genes inherited from oocyte.