The transgenic construct consists of a 370kb YAC insert that includes the entire human FXN gene with GAA triplet repeat sequences, and was injected into fertilized CBA X C57BL/6 hybrid fertilized oocytes. Founder line YG22 was generated, showing a reduced transmission rate of 21%, indicating germ-line mosaicism of the transgene, compared to 52% transmission to offspring for founder line YG8. One copy of the FXN gene was detected, and contains a single 190 GAA repeat sequence.