Final answer:
If multiple sperm fused with an egg, a condition known as polyspermy would occur, leading to a genetically abnormal zygote with extra sets of chromosomes. This triploid zygote would be incompatible with life and is not viable. Sophisticated biological mechanisms during fertilization prevent multiple sperm from penetrating the egg to ensure a normal diploid zygote.
Step-by-step explanation:
What Would Happen If Multiple Sperm Fused With One Egg?
If multiple sperm were to fuse with a single egg, a condition known as polyspermy would occur, resulting in a genetically abnormal zygote. During normal fertilization, hundreds of capacitated sperm reach the oocyte, and only one is meant to penetrate the egg, thanks to the protective layers of the corona radiata and zona pellucida. The first sperm that successfully fuses triggers a cortical reaction to block any subsequent sperm from penetrating, thus ensuring the creation of a diploid zygote, which is vital for the development of a viable embryo.
However, if this mechanism fails and multiple sperm cells enter the egg, an abnormal triploid—or even higher ploidy—organism could form. This is because the zygote would have extra sets of chromosomes, making it incompatible with life. Such embryos are not viable and are typically reabsorbed or miscarried early in development. The fast and slow blocks to polyspermy, identified as changes in membrane potential and structure, are critical to prevent this from occurring. When the process functions as intended, it ensures the success of fertilization, leading to the development of a healthy embryo.