Human embryo after zona drilling

Human embryo after zona drilling

Color-enhanced scanning electron micrograph of a human embryo at day 3. The egg has been fertilized in vitro and has developed to this stage in culture. The coat around the egg (zona pellucida) has been treated with acid Tyrodes solution to make a hole so an individual cell can be removed. This cell can then be used for genetic diagnosis before the embryo is transferred to the woman’s uterus. This allows the selective implantation of embryos that do not carry the genetic disease in question.