Analysis of a Developmental Pathway: Many transgenic animals are non-viable, either prenatally or perinatally. This can give insights into genes essential for during development. Correlation of time of embryonic lethality to known animal embryonic gene expression patterns provides knowledge of insight into the pathways and interaction of the mutated gene. Information on gene expression can easily be obtained by using a reporter gene, which combines the regulatory regions of the gene under study with an easily detectable marker protein. For e.g. – Using Cre-lox system both temporal and tissue specific control of expression of knockout gene construct can be studied.
Modification of Animal Anatomy and Physiology: Transgenic technology can be used for genetic improvement of an animal. A foreign gene can be introduced by selective deletion of endogenous gene or specific region. A direct approach is to add a gene for a growth factor or hormone to the genome instead of altering the complex multigenic physiology of the mammal. For developing animals with novel disease resistance, higher yield of meat or milk, decreased body fat, etc.
Production of Organs for Xenotransplantation: Transplantation of living cells, tissues or organs from one donor organism to another receipient organism is known as xenotransplantation. Such cells, tissues or organs are called xenografts or xenotransplants. The shortage of healthy donor organ can be mitigated by developing animals whose organs would be suitable for xenotransplantation. Transgenic animals have aided the understanding of molecular basis of graft rejection, which includes foreign antigens, coagulation defects and interspecies ligand-receptor interactions. e.g. - Transgenic pigs have been developed that do not express the surface glycoproteins highly immunogenic to humans.