By a process of genetic backcrossing, DNA from a chromosomal segment of one mouse strain is inserted into the homologous region of another mouse strain.

Gradual diffusion of genes from one population to another through hybridization.

The incorporation of genetic material from one species into another. The term was originally coined in connection with the directed transfer of useful genes from wild relatives to crop plant species. Recently the term ‘transgene introgression' has been used in connection with the inadvertent transfer of genetic material from transgenic crops to wild relatives. In each case introgression requires the production of a fertile hybrid between a crop plant and a wild relative with subsequent backcrossing either to the crop plant species or the wild species.

The act of going in; entrance.