From fertilizationto cleavageFirst cleavage in the sea urchin embryoMammalian fertilization: a 3-min group activityYou are mating a female mouse homozygousfor a null mutation in ZP3 gene to a wild-type male. Which fertilization defects areyou expecting to observe and why?A. Each egg will be fertilized by multiple sperm(polyspermy)B. The sperm will fail to penetrate zona pellucidaand no fertilization will occurC. Fertilization will occur, but the embryo will notbe viableD. No effectStage 3: fusion of genetic materialQ. Which of the pronuclei is the paternal one?Resumption of protein and DNAsynthesis in the eggResumption of DNA synthesisInactivation of MAP kinaseIntitiation of cell divisionTranslation of cyclin BResumption of protein translation:histones, tubulins, actins,morphogenetic factorsDegradation of inhibitors of translation:4E-binding proteinCa2+ influx(pH increase)The accelerated cell cycle in earlyamphibian blastomeres: what’smissing?First cleavage in the sea urchin:Louise Brown - the first IVF baby,England, 197821.8 In vitro fertilizationEgg harvestCleavageSparce, evenlydistributed yolk: seaurchins, mammalsYolk concentrated atone pole: amphibiansMeroblastic cleavage,dense yolk throughoutmost of the egg: fish,reptile, birdsComplete (holoblastic) cleavageIncomplete (meroblastic) cleavageWhat if you have dense yolk inthe middle of the egg?Insects: superficial cleavageMovie: cleavage inamphibianshttp://www.xenbase.org/xenbase/original/atlas/movies/lotscleavmov2.movBy the end of the cleavage stage, theembryo is a blastula (a hollow ball ofcells)Blastomeres BlastocoelBlastomeres look very similar to each other (except for the yolk content)Axes of a bilaterally symmetricalanimalHow much do blastomeres“know” about their final fate?Groups:Suggest an experiment that will testwhether a particular cell/group of cellswill always end up in the