Practice question

Wingless gene product is secreted glycoprotein lipid-modified by Porcupine acyltransferase, orthologous to vertebrate Wnt1 originally identified as integration site for mouse mammary tumor virus and as wingless in Drosophila. Wg binds Frizzled and co-receptor Arrow/LRP, inhibiting beta-catenin destruction complex allowing Armadillo nuclear translocation activating target genes. Vertebrate Wnt family controls axis patterning, limb development, and stem cell maintenance. Sonic Hedgehog belongs to Hh family, Notch to distinct juxtacrine receptor family, BMP to TGF-beta family, making Wnt specific homolog. Conservation underscores central role of Wg/Wnt signaling in segment polarity, midbrain-hindbrain organizer formation, and oncogenesis mechanisms.