Moreover, the ability to manipulate many millions of cells at once will allow us to use homologous recombination to perform much more specific genetic modifications of farm animals. These will include the deletion or substitution of specific genes or the introduction of the single letter changes in the whole of the genetic code that are characteristic of many human genetic diseases. Ian Wilmut describes some of the possible applications.
Human proteins are in great demand for the treatment of a variety of diseases.
Small quantities of human proteins can be produced in cell culture but costs are very high. Much larger quantities can be produced in bacteria or yeast but the proteins produced can be difficult to purify and they lack the appropriate post-translational modifications that are needed for efficacy in vivo . In the US, Genzymc Transgenics have focused on using goats and they too have products in clinical trials. Producing transgenic animals by nuclear transfer has immediate practical advantages, It uses less than half of the experimental animals to generate founder animals than does pronuclear injection. By specifying the sex of the offspring and generating a small number of identical clones, it is possible to generate a flock that is sufficiently large for clinical trials within one and half years.