system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: So there are dominant and recessive genes.  Why is the recessive gene recessive?

What makes the dominant gene dominant?
gpt
Say that the first version of the gene produces X protein, and the second version does not. If you have any copy of the first version, your body will have some X; the only way you can end up with no X is if you get two copies of the second version. 

Now, if your body has some process that doesn't care about how *much* X you have, but only whether or not X is present, the first version will be dominant and the second will be recessive.