In order to prevent polyspermy and minimise the possibility of producing a triploid zygote, several changes to the egg's zona pellucida renders them impenetrable shortly after the first sperm enters the egg.
In order to prevent polyspermy and minimise the possibility of producing a triploid zygote, several changes to the egg's cell membranes renders them impenetrable shortly after the first sperm enters the egg.
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