You could build houses from bricks, timber or poured concrete that all looked the same in the end. Their internal structures and methods of construction would be different, but they would have the same form.
I'm reading the GP's comment similarly.
genes are instructions for building proteins.
For a given output, you could write a program in wildly different programming languages, or even use the same language but structure it in wildly different ways.
If there's no match for the source code (genes), then find a match for the output (protein).
Source: Am structural biochemist