Practice question

Mammalian zygote requires centrosome to assemble mitotic spindle for first cleavage. Human oocyte lacks functional centrioles after pachytene elimination, so paternal contribution is essential. Proximal centriole introduced by sperm at fertilization recruits maternal pericentriolar material including gamma-tubulin, pericentrin and centrin to regenerate functional centrosome. This centrosome duplicates and nucleates microtubules organizing syngamy and first bipolar spindle aligning parental genomes. Without sperm centriole, parthenogenetic embryos often display abnormal spindles. It does not mediate zona digestion or mitochondrial energy production, but provides microtubule organizing center initiating embryonic cell divisions and polarity establishment.