The present invention provides for the production of homozygous primary cells that carry a specific transgenic integration of interest on both chromosomes by bypassing breeding. These cell lines can they be used for the accelerated production of homozygous transgenic animals by somatic cell nuclear transfer. The invention is thus useful in the production of transgenic ungulate animals capable of producing desired biopharmaceuticals in their milk at higher yield than a comparable heterzygote. By combining the selection techniques of the current invention with somatic cell nuclear transfer it can be applied to large animals, where there is a strong need to shorten the time to homozygosity.