That's not how selective breeding works. There's no rule where it takes one generation per gene. With a large population you can find individuals who gain many

That's not how selective breeding works. There's no rule where it takes one generation per gene. With a large population you can find individuals who gain many generic improvements in one generation. With sexual reproduction you can combine advantageous gene lines. Finally, note that we're starting with a huge amount of diversity so we don't need to create new genes, just select the best ones we already have.