In many vertebrate and invertebrate species, a specialized cytoplasmic region of the egg or the zygote that contains germ-cell determinants and other maternal products required for normal development in the early embryo. The cytoplasm located at the posterior pole of Drosophila and the vegetal pole of Xenopus embryos are examples of pole plasm. In Drosophila, several maternal effect genes involved in pole plasm formation have been identified and are known as grandchildless genes (q.v.). Females carrying mutations in these genes produce embryos that lack polar granules (q.v.) and show other developmental defects. See cytoplasmic determinants, cytoplasmic localization, maternal effect gene, maternal polarity mutants.
Subjects: Genetics and Genomics.