Practice question

PAR proteins are partitioning defective regulators of polarity highly conserved from nematodes to mammals. PAR-3 forms anterior cortical complex with PAR-6 and atypical PKC, anchoring CDC-42 and NMY-2 myosin. PAR-1 MARK kinase and PAR-2 occupy posterior cortex after sperm centrosome signal suppresses anterior contractility and enables posterior recruitment. Mutual exclusion maintained via phosphorylation, so PAR-1 excludes PAR-3 posteriorly and aPKC excludes PAR-1 anteriorly. PAR-3 establishes anterior identity, recruiting centrosome rotation cues and influencing segregation of MEX-5, PIE-1, P-granules, ultimately orchestrating asymmetric division, spindle orientation and embryonic axis formation.