Scientists Edit Human Embryo Genes With Startling Precision - The New York Times

image: DNA Typewriter is injected into the genetic material of a fertilized mouse egg. This technology taps into the genetic material in the fertilized egg and resulting embryonic cells as a recording device of the cells' histories. It tracks their relationships as the embryo develops. Scientists have succeeded in reconstructing the family tree of cells in a developing mouse embryo. They recorded cells’ relationships, starting when the fertilized egg first split in two and ending after the body with organs took shape. That period lasted 13.5 days. (Full gestation in mice is 19 to 21 days.)