Practice question

Avian egg experiences extensive rotation while transiting oviduct, influenced by gravity orientation, albumen secretion and shell deposition. Physical rotation generates asymmetry in blastoderm attached to vitelline membrane, causing posterior marginal zone to form at side experiencing highest shear and establishing pH differences between blunt and pointed poles. Experimental manipulation tilting eggs alters streak position, proving gravity-dependent rotation breaks symmetry. Unlike amphibian sperm entry, fertilization internal, and unlike fish maternal RNAs, this mechanical rotation provides initial anterior-posterior axis bias before molecular signals from Koller's sickle take over.