- Oogenesis (the creation of an ovum, an egg cell) takes one cell and makes four. But only one cell is eventually used as a gamete. It would be inefficient to allow the three other cells equal amounts of cytoplasm or nutrients if only one of those cells is the important one. Therefore, all resources from the original cell goes to the ovum, while the three other cells are just a depository for DNA. The three other cells are called polar bodies and will then die soon after.
Sexually transmitted diseases (STDs) are caused by infections that are passed from one person to another during sexual contact.
These infections often do not cause any symptoms. Medically, infections are only called diseases when they cause symptoms. That is why STDs are also called "sexually transmitted infections." But it’s very common for people to use the terms "sexually transmitted diseases" or "STDs," even when there are no signs of disease.