Human eggs lack centrioles, so the father's sperm must supply them
A human egg carries no centrioles at all. At fertilisation the sperm contributes two structurally different ones, and they build the embryo's first centrosome, the hub that organises microtubules so the parents' genetic packages can meet and the first cell divisions can begin. Without that paternal gift, development would stall.
A centriole is a small cylinder made mostly of the protein tubulin, its name meaning little central part because it usually sits near the middle of the cell. The classic design is nine sets of three short microtubules arranged in a ring, though fruit fly embryos and crabs use nine doublets and the worm C. elegans nine singlets. Two centrioles at right angles, wrapped in dense pericentriolar material, form a centrosome, the cell's main microtubule-organising centre.
Centrioles help arrange the spindle that separates chromosomes during division and help finish splitting the cell. Yet they are less indispensable than once believed: cells whose centrioles are destroyed by laser can still progress and later build new ones from scratch, and mutant flies lacking them develop normally, though they have no cilia or flagella and die soon after birth. Each cell duplicates its centrioles exactly once per cycle, in step with DNA replication, with a new one sprouting at right angles from each existing one.
Their other big job is making cilia and flagella. The older, mother centriole becomes the basal body anchoring these hair-like structures. Correctly positioned cilia in the early embryo help establish which side of the body is left and which is right, and failures of centriole migration before cilia form have been linked to Meckel-Gruber syndrome.
The history spans the late 19th century. The centrosome was found independently by Walther Flemming (1875) and, a year later, by Edouard Van Beneden, Van Beneden saw its paired structure in 1883, and Theodor Boveri coined centrosome in 1888 and centriole in 1895. The last common ancestor of all eukaryotes had them, but conifers and flowering plants have lost them completely, and other land plants keep them only in swimming male sex cells.
Source: Centriole
