system
Given the following post, respond as if you're commenting on Reddit:
human
Why are some alleles more dominant than others?

This has always confused me. Why is a brown haired gene more dominant than a blonde hair gene, etc? I know that when it comes to human genes, there's a lot of multi-alleled non-Mendellian stuff going on, but I'm just curious as to why some alleles are dominant and some are recessive.
gpt
The dominant gene codes for a functional protein.  The recessive gene codes for a non-functional protein or no protein at all.  

Brown hair is brown because there is pigment because there's a gene that codes for a protein that makes the pigment.  If there gene doesn't code for a functional protein, no pigment makes it to the hair, so it is pigmentless, aka blonde.  The gene is dominant because if even just one allele codes for the functional protein there's still pigment being made.  Same thing with blue/green eyes vs brown, yellow peas vs green, etc - the 'colored' version is the dominant trait as a result of a single or double copy of a functional color-producing protein while the 'colorless' version is the recessive trait from a complete lack of color-producing protein.