Like what makes a dominant trait different than recessive, if it’s all in DNA shouldn’t our body just choose one or the other?
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Most genes produce proteins, and those proteins do something in the body.
In a dominant gene, the variant is usually *producing* a protein that does something (often something it’s not supposed to, if it’s not a normal gene). The other copy can make the normal protein, but the altered and functional version of it is doing something else regardless.
In a recessive gene, on the other hand, the variant is usually *breaking* a protein so that it *doesn’t* do what it normally would. But since the other copy can still make functional proteins, it can make up for the broken versions produced by the recessive gene. (One thing this suggests, and which is true, is that you might show effects of having a recessive gene even if you don’t have two of them. For example, someone who has one copy of the gene for sickle cell disease has enough of the altered proteins that their red blood cells are shaped a little differently, which gives them resistance to malaria [which can’t infect the oddly-shaped cells].)
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