Most mutations are irrelevant or don't impact anything until they're duplicated enough times to matter.

For example, every human has 6 to 24 copies of the genes that let us digest wheat: AMY1 (salivary) AMY2A / AMY2B (pancreatic).

If any one or two of those mutate in the next generation, it won't be noticeable or make any sort of impactful change.

This is why changes from one species to another take hundreds of thousands of years (many generations). A whole lot of people will need to accumulate the same mutations and survive (or just reproduce) with those changes (when others don't) for speciation to occur.

About 70,000 years ago, nearly all humans on earth died, leaving behind just a few tens of thousands (maybe up to 200,000) that had just the right combinations of genes to survive. When that happened, humanity lost nearly all of its genetic diversity. It'll be a long time before we diversify again (if we ever make it that far).

That's the thing about sci-fi, it's a warning about potential horrors but that doesn't mean horrifying things can't have a positive.

I wholly understand that the point of gataca is oppression that comes from giving humans another metric to oppress. It's spelt out plainly. Unfortunately, like the main character, I'm also the product of people who didn't think about what they'd be passing on. Now in my thirties, I'm in the early stages of arthritis, my eyes are failing, and if family tradition holds I'll have less than a decade before a sudden and undetectable heart condition kills me. If that doesn't get me I have early dementia waiting in line.

I'm three quarters through the life I was given and I knew the name of my killer before I was ten. To me, Gataca is a world where some forethought on my parents would mean never having to do weekly injections so that my flesh does not consume itself. A long and ordinary life without pills every morning or regulating my diet for inflammation.

SciFi isn't about the dangers of science, it's about the dangers of science misused. The moral of gataca is that people are more then the sum of their parts and to value them on such is cruel and unjust. It's that parents have a responsibility to their children, regardless of their own feelings on it. But it's moral isn't that correcting bad genetics is wrong. No one deserves to be born broken.

Ok lets say you have a child. And they tell you he or she won't last past 25 years old, but they can make an "adjustment" so he or she can live a full and happy life.?