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| Modern Genetic Analysis Chapter 11. Applications of Recombinant DNA Technology Recombinant DNA Technology in Eukaryotes Figure 11-18. Production of a pharmaceutically important protein in the milk of transgenic sheep. The gene of interest encodes a protein that is of therapeutic importance, such as tissue plasminogen activator used to dissolve blood clots in humans. The gene is placed under control of the b -lactoglobulin promoter, active only in mammary tissue, and is introduced into sheep ova by microinjection of the expression vector into the nucleus. The injected ova are implanted into foster mothers, and progeny expressing the transgene are identified by PCR amplification of chromosomal DNA by using primers from the sequence of the gene of interest. Transgenic sheep express this gene only in mammary tissue and secrete high levels of the gene's protein into the milk, from which it can be purified.

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