put gene into

Only nature puts gene (generation) into being at inception of life...what beings put into each other represents the dying particles of another being as ballast. Why? To distract each other from regeneration.

pig into lettuce

That's called gene-splicing...gene implies nature splitting each native from one another; splicing implies artificially joining the split back together.

Gene implies all moving through each one...splicing tempts one to ignore that with each joined burden from one another.

inserted a copy

There can be only one origin (nature) for each copy (native) inserted within...

next generation

There can be only one generator (inception towards death) for each reactor (life) within...next/nekh - "near; narrow" implies each beings narrow path as next in line.