Genetic Engineering, Animals

Abstract

Abstract Embryo splitting and cloning by nuclear transfer are methods to mass‐produce identical copies of a single embryo or a single adult animal. A transgenic animal may have a stable modification, a stable deletion, or a stable insertion of a foreign gene into its genome. Transgenic animals can be classified as traditional transgenics where a gene is inserted at a random location in the genome or gene‐targeted transgenics (knock‐outs, knock‐ins, and conditional knock‐outs) where a specific gene within the genome is modified. Traditional transgenics are created by pronuclear microinjection, retroviral infection, sperm‐mediated gene transfer, or nuclear transfer. Gene targeting is done by using embryonic stem cells (mice) or somatic cells (farm animals). A DNA targeting vector is constructed that is designed to insert itself into the embryonic genome and inactivate a specific gene. Transgenic and gene targeted animals have become mainstays for scientific research. Transgenic farm animals are essential for the low‐cost production of recombinant proteins. The productivity of farmers may be improved through the use of transgenic farm animals. Pigs with deleted immune recognition genes may soon provide organs for transplantation into humans. Transgenic and gene targeted mice represent some of the most important tools for biomedical research in the twenty‐first century. To understand the function of a specific gene, a transgenic mouse is created that overexpresses the gene. Gene targeting is a step beyond simple overexpression of genes because the function of a gene is accessed by evaluating the phenotype of the gene‐deleted mouse. Conditional knock‐out mice may represent the final step in the evolution of genetic modification of animals.