Abstract: Materials and methods for producing fibrinogen in transgenic non-human mammals are disclosed. DNA segments encoding A.alpha., B.beta. and .gamma. chains of fibrinogen are introduced into the germ line of a non-human mammal, and the mammal or its female progeny produces milk containing fibrinogen expressed from the introduced DNA segments. Non-human mammalian embryos and transgenic non-human mammals carrying DNA segments encoding heterologous fibrinogen polypeptide chains are also disclosed.

Abstract: A method of producing a proteinaceous compound, involves incorporating a DNA sequence coding for a polypeptide chain of said compound into a gene of a mammal (such as a sheep) coding for a milk whey protein in such a way that the DNA sequence is expressed in the mammary gland of the adult female mammal. The proteinaceous compound may be a (optionally modified) protein such as a blood coagulation factor. The DNA sequence is preferably inserted into the first exon of a gene coding for a whey protein such as beta-lactoglobulin. The proteinaceous compound will generally be recovered from milk of the female mammal, but may (for example if it is an enzyme) be used in situ.