Chapter49 - Chapter 49 1 Fertilization i Fertilization...

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Chapter 49 1) Fertilization i) Fertilization involves four events (1) The sperm contacts the egg and recognition occurs. (2) The sperm or sperm nucleus enters the egg. (3) The egg becomes activated and developmental changes begin. (4) The sperm and egg nuclei fuse. b) The first step in fertilization involves contact and recognition. i) Eggs are active in fertilization. ii) Coverings facilitate fertilization as well as no fertilization by sperm of the wrong species. iii) Outside the plasma membrane of the sperm, there is a thin vitelline envelope , and a thick glycoprotein jelly coat . iv) The egg secretes chemical substances the draw sperm to it. v) When a sperm contacts an egg, it undergoes an acrosome reaction , in which the acrosome membrane fuses and enlarges its pores. vi) If the species of sperm and egg are the same, bindin , a species-specific protein adheres the egg + sperm. vii)Before a sperm partakes in fertilization it must first undergo capacitation , a maturation process in the female reproductive tract. viii) This allows sperm to have their acrosome reaction and makes them more motile. c) Sperm entry is regulated i) In the FAST BLOCK to polyspermy, the egg membrane depolarizes, and no more sperm can bind to it. ii) In the SLOW BLOCK to polyspermy, which can take 7 minutes, the cortical reaction bring calcium ions into the cell to enlarge the space between the two membranes and make it impossible for more sperm to get in. iii) The vitelline envelop ^ becomes elevated from the plasma membrane.
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Chapter49 - Chapter 49 1 Fertilization i Fertilization...

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