25. Mixing sperm and egg in a petri dish results in fertilization. We discussed
ID: 146321 • Letter: 2
Question
25. Mixing sperm and egg in a petri dish results in fertilization. We discussed modified in vitro culture conditions that increase the chance of obtaining polyspermy. What are those culture conditions? (2 points) 26. Immunohistochemical staining of -catenin is a common method to determine whether the Wnt pathway is active. If Wnt is present, and the pathway is active, in which part of the cell (example, plasma membrane, endoplasmic reticulum) would exhibit fluorescence in an immunohistochemical stain for B-catenin? (2 points) 27. Following the translation of hedgehog mRNA into Hedgehog protein, the protein undergoes two important post-translational modifications that aid in its secretion from the cell and its binding to its receptor on the surface of an adjacent cell. What are these modifications? (4 points) #2.Explanation / Answer
Answer 25: Polyspermy is the condition when there is more then one male sperm to fertilize the single female cell or the cells in polyspermy contains three or more copy of chromosomes one from egg and other from one from each multisperm. During the process of developmental biology several sperms reach to the membrane of zona pelliucida but only one will bind to egg membrane . sperm bind EP3 at the post of coronal region and start to penetrate the zona pellucida to reach the egg membrane. now binding of sperm to egg membrane will iniciate the influx of extracellular Sodium ion inside the cytoplasm which causes the depolarization of egg so influx of sodium ion ct as the fast block of extra sperm entry in egg cell. and the other mechanism is called as slow block which begins when calcium ion enter the egg from the para vigilant spacetrigerring egg phychosis of cortical granules to modify EP3 glycoprotein making the zona pellucida impermeable to sperm. so in invitro conditions the influx of ion that is the activity of depolarization is of concern which can be altered by electric current or changing the buffering capacity so that polyspermy can be induced.
Answre 26) Wnt is a signaling molecule present outside the nucleus into cytosol which is surrounded by plasma membrane but it we talk more specifically then we can say yes it is ER part where Wnt is first bind but all other activators are found in different region of cell.If wnt is present then it binds with Frizzled which will activate and bring the receptor LRP close together so they together provide a signal to Dishevelled .which prevent the hydrolysis of beta catenin by destructive complex which is made up of GSK3,Axin, CK1 ,APC and DVL molecules .So as the activity of distructive complex is blocked by beta catenin complex this beta catenin enter the nucleus and contact directly with TCF and LEF complex by which Grocho will released so that transcription will be carried out to synthesize the mRNA molecule . use your concern book to view the mechanism.
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