The general procedure for cryopreservation of gametes is as follows:
1. Collection: The gametes are collected from the donor. This can be done through a variety of methods, depending on the type of gamete. For example, sperm can be collected through masturbation or a surgical procedure, while eggs can be collected through transvaginal aspiration.
2. Preparation: The gametes are then prepared for cryopreservation. This may involve washing them to remove debris, and then adding a cryoprotectant, which is a substance that helps to protect the cells from damage caused by freezing.
3. Freezing: The gametes are then slowly cooled to a very low temperature, typically -196 degrees Celsius (-321 degrees Fahrenheit). This is done in a controlled manner to prevent the formation of ice crystals, which can damage the cells.
4. Storage: The gametes are then stored in liquid nitrogen tanks or other long-term storage devices.
5. Thawing and insemination: When the gametes are needed for reproduction, they are thawed and fertilized in vitro (outside the body). The resulting embryos are then transferred into the uterus of the recipient mother.
Cryopreservation of gametes is a highly successful procedure, and the vast majority of cells survive the freezing and thawing process. This makes it a valuable tool for preserving fertility and for conservation of endangered species.