This question is courtesy of my ten year old daughter who meant to search “cornception” on YouTube but got autocorrected to “conception.” The videos that came up were fortunately educational in nature. Thanks for reading this far!
In: Biology
A human egg is surrounded by a protein matrix “shell” called a zona pellucida. This layer has special docking sites called ZP2 proteins that a sperm can “see” and attach to. Once one sperm gets in to the egg and fertilization occurs these docking sites fall off, and the matrix shell changes and hardens, making it difficult for more sperm to try and enter the egg. Secondly, an egg, like all cells has a membrane around it that selectively allows some things in, After fertilization, it “depolarizes” which means it changes its electrical charge so it is difficult for more sperm to get inside, even if they made it past the first barrier. It is not a foolproof system and sometimes extra sperm get in, creating a condition called polyspermia. Around 10% of spontaneous abortions are due to triploidy , the presence of an extra set of chromosomes in a fetus, usually caused by polyspermy
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