Why does only one sperm cell get to fertilize the egg? How is multi-sperm fertilization prevented and does this prevention ever fail?
In: 10
The first way the egg makes sure only one sperm enters is by slowing down the sperm with the cumulus oophorus. Think of it like a thick wall that the sperm has to break through. Almost instantaneously when a sperm enters the egg the egg undergoes a dramatic change where the membrane becomes impenetrable no longer letting anymore sperm to enter. It’s VERY rare but sometimes two sperm meet the egg at the exact same time and they both enter. Having 3 sets of chromosomes isn’t viable for life so eventually the cells will die from the error. There is one case I could find from [2019](https://www.bbc.com/news/health-47371431) where two sperm fertilized one egg but the twins got very lucky that the egg was able to divide into two embryos each with 2 sets of chromosomes. I cannot emphasize how rare this is! Most of the time the body’s process for conception goes by perfectly and one egg and one sperm create the perfect 2 sets of chromosomes.
Latest Answers