Animal Sciences Department, Agricultural College, Khorasgan Branch, Islamic Azad University, Khorasgan, Iran
Cell and Molecular Biology Department, Royan institute for Animal Biotechnology, ACECR, Isfahan, Iran
Biology Department, School of Sciences, University of Isfahan, Isfahan, Iran
Reproduction and Development Department, Royan institute for Animal Biotechnology, ACECR, Isfahan, Iran
Biology Department, School of Sciences, Islamic Azad University, Marvdasht Branch, Marvdasht, Iran
Over the past two decades, many approaches for transferring genes into the genome of domestic animals have been devised. The main purposes of transgenesis are: to increase animal capabilities, to knock down or silence both onco-genes and deleterious genes, and to produce a pharmaceutical protein. Transgenesis techniques include pronuclear microinjection (PNM), somatic cell nuclear transfer (SCNT), viral infection (VI) and sperm-mediated gene transfer (SMGT). The first transgenic mouse was produced by using the PNM technique and transgenic animals from other species (rabbit, sheep, pig and cattle) have been produced thereafter. However, the PMN technique had certain drawbacks: low efficiency, random integration site of the transgene and a high mosaic rate. For this reason, other alternative techniques have been devised to overcome its drawbacks. The most reliable method for transgenesis which bypasses mosaics is SCNT. However, this method is complicated and tedious; with multiple stages that need setting up. VI has been used to transfer genes into the oocytes and zygotes with high efficiency and versatility. In spite of its simplicity, the maximum transgene length should be less than 8.5 kb. Currently, spermatozoa are considered as an alternative method of carrying transgenes into the oocytes with minimum technical demands. In contrast to VI, SMGT is being used successfully to transfer different kinds of BACs with more than 200 kbp into mouse oocytes. The present review summarizes the methods by which transgenes can be introduced into zygotes of domestic animals.