The transgenic blastocyst develops into a transgenic mouse that
is heterozygous for the recombinant gene. Heterozygous mice are
mated with other heterozygotes and mice homozygous for the
recombinant gene are identified.

A recombinant gene with the neomycin gene inserted into the
middle of the gene to be knocked out is created.

A selection strategy is employed to select for those ES cells
that have taken up the recombinant gene and in which a
recombination event has occurred.

The transgenic ES cells are injected into a blastocyst which is
implanted into a pregnant female mouse.

The recombinant gene is inserted into ES cells