Nuclear-donor cat and cloned kitten with its surrogate mother. a, Adult female cat that supplied cumulus cells for nuclear transplantation. The cells were cultured in DMEM/F12 medium for 5 days at 37 °C until confluent; micromanipulation was used to enucleate ova obtained after routine ovariohysterectomy and to transfer the donor's cumulus cells into the perivitelline space. Enucleated ova and cumulus cells were fused by electrofusion; a second electropulse was applied to activate the oocytes. b, The surrogate mother, a synchronized recipient of three cloned embryos, produced one cloned kitten, which was delivered by caesarian section 66 days after embryonic transfer. For further details, see supplementary information.